Ribbon diagram of the catalytically perfect enzyme TIM.

An enzyme is a protein that catalyzes, or speeds up, a chemical reaction. The word comes from the Greek ένζυμο, énsymo, which comes from én ("at" or "in") and simo ("leaven" or "yeast"). Certain RNAs also have catalytic activity, but to differentiate them from protein enzymes, they are referred to as RNA enzymes or ribozymes. Image File history File links Ribbon diagram of triose-phosphate isomerase. ... Image File history File links Ribbon diagram of triose-phosphate isomerase. ... (Fig. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A catalyst (Greek: καταλύτης, catalytÄ“s) is a substance that accelerates the rate (speed) of a chemical reaction (see also catalysis). ... A chemical reaction is a process that results in the interconversion of Chemical substances . ... Leaven is a raising agent for bread. ... Yeasts constitute a group of single-celled (unicellular) fungi, a few species of which are commonly used to leaven bread , ferment alcoholic beverages, and even drive experimental fuel cells. ... Ribonucleic acid (RNA) is a nucleic acid polymer consisting of covalently bound nucleotides. ... A ribozyme (from ribonucleic acid enzyme, also called RNA enzyme) is an RNA molecule, that catalyzes a chemical reaction. ...

Enzymes are essential to sustain life because most chemical reactions in biological cells would occur too slowly, or would lead to different products, without enzymes. A malfunction (mutation, overproduction, underproduction or deletion) of a single critical enzyme can lead to a severe disease. For example, the most common type of phenylketonuria is caused by a single amino acid mutation in the enzyme phenylalanine hydroxylase, which catalyses the first step in the degradation of phenylalanine. The resulting build-up of phenylalanine and related products can lead to mental retardation, if the disease is untreated. Life is a multi-faceted concept that may refer to the ongoing process of which living things are a part the period between the conception (the point at which the entity can be considered to be an individualized being) and death of an organism the condition of an entity between... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ... Phenylketonuria (PKU) is a human genetic disorder, in which the body lacks phenylalanine hydroxylase, the enzyme necessary to metabolize phenylalanine to tyrosine. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... Categories: Biochemistry stubs | EC 1. ... The alpha-amino acid Phenylalanine exists in two forms, the D- and L- forms, which are enantiomers (mirror-image molecules) of each other. ... Mental retardation (also called mental handicap and, as defined by the UK Mental Health Act 1983, mental impairment and severe mental impairment) is a term for a pattern of persistently slow learning of basic motor and language skills (milestones) during childhood, and a significantly below-normal global intellectual capacity as...

Like all catalysts, enzymes work by lowering the activation energy of a reaction, thus allowing the reaction to proceed much faster. Enzymes may speed up reactions by a factor of many millions. An enzyme, like any catalyst, remains unaltered by the completed reaction and can therefore continue to function. Because enzymes, like all catalysts, do not affect the relative energy between the products and reagents, they do not affect equilibrium of a reaction. However, the advantage of enzymes compared to most other catalysts is their sterio-, regio- and chemoselectivity and specificity. This article needs to be cleaned up to conform to a higher standard of quality. ... Equilibrium or balance is any of a number of related phenomena in the natural and social sciences. ...

Enzyme activity can be affected by other molecules. Inhibitors are naturally occuring or synthetic molecules that decrease or abolish enzyme activity; activators are molecules that increase activity. Some irreversible inhibitors bind enzymes very tightly, effectively inactivating them. Many drugs and poisons act by inhibiting enzymes. Aspirin inhibits the COX-1 and COX-2 enzymes that produce the inflammation messenger prostaglandin, thus suppressing pain and inflammation. The poison cyanide inhibits cytochrome c oxidase, which effectively blocks cellular respiration. An inhibitor is a type of effector (biology) that decreases or prevents a chemical reaction. ... Aspirin or acetylsalicylic acid is a drug in the family of salicylates, often used as an analgesic (against minor pains and aches), antipyretic (against fever), and anti-inflammatory. ... Cyclooxygenase (COX) is an enzyme (EC 1. ... Cyclooxygenase (COX) is an enzyme (EC 1. ... Inflammation is the first response of the immune system to infection or irritation and may be referred to as the innate cascade. ... A prostaglandin is any member of a group of lipid compounds that are derived from fatty acids and have important functions in the animal body. ... A cyanide is any chemical compound that contains the cyano group C≡N, with the carbon atom triple-bonded to the nitrogen atom. ... Cytochrome c oxidase The enzyme cytochrome c oxidase (PDB 2OCC, EC 1. ... Cellular respiration is the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. ...

While all enzymes have a biological role, some enzymes are used commerically for other purposes. Many household cleaners use enzymes to speed up chemical reactions ( i.e., breaking down protein or starch stains in clothes).

More than 5,000 enzymes are known. Typically the suffix -ase is added to the name of the substrate (e.g., lactase is the enzyme that catalyzes the cleavage of lactose) or the type of reaction (e.g., DNA polymerase catalyzes the formation of DNA polymers). However, this is not always the case, especially when enzymes modify multiple substrates. For this reason Enzyme Commission or EC numbers are used to classify enzymes based on the reactions they catalyze. Even this is not a perfect solution, as enzymes from different species or even very similar enzymes in the same species may have identical EC numbers. The word substrate can mean the following: In biochemistry, a substrate is a molecule which is acted upon by an enzyme. ... Lactase is a member of the β-galactosidase family of enzyme: enzymes that hydrolysis β 1,4 bonded attachments off of galactose. ... Lactose is a disaccharide that makes up around 2-8% of the solids in milk. ... DNA polymerase 3D structure. ... EC numbers (Enzyme Commission numbers) are a numerical classification scheme for enzymes, based on the chemical reactions they catalyze. ...

Etymology and history

Eduard Buchner

The word enzyme comes from Greek: "in leaven". As early as the late 1700s and early 1800s, the digestion of meat by stomach secretions and the conversion of starch to sugars by plant extracts and saliva were observed. 19th century (or early 20th century) photograph. ... 19th century (or early 20th century) photograph. ... Eduard Buchner (May 20, 1860 -- August 12, 1917) was a German chemist and zymologist, the winner of the 1907 Nobel Prize in Chemistry for his work on fermentation. ... Events and trends The Bonneville Slide blocks the Columbia River near the site of present-day Cascade Locks, Oregon with a land bridge 200 feet (60 m) high. ... Events and Trends Beginning of the Napoleonic Wars (1803 - 1815). ... Meat is animal tissue (mainly muscle) used as food. ...

Studying the fermentation of sugar to alcohol by yeast, Louis Pasteur came to the conclusion that this fermentation was catalyzed by "ferments" in the yeast, which were thought to function only in the presence of living organisms. In its strictest sense, fermentation (formerly called zymnosis) is the anaerobic metabolic breakdown of a nutrient molecule, such as glucose, without net oxidation. ... Louis Pasteur (December 27, 1822 – September 28, 1895) was a French microbiologist, chemist and humanist. ... Vitalism is the doctrine that life cannot be explained solely by mechanism. ...

In 1897, Hans and Eduard Buchner inadvertently used yeast extracts to ferment sugar, despite the absence of living yeast cells. They were interested in making extracts of yeast cells for medical purposes, and, as one possible way of preserving them, they added large amounts of sucrose to the extract. To their surprise, they found that the sugar was fermented, even though there were no living yeast cells in the mixture. The term "enzyme" was used to describe the substance(s) in yeast extract that brought about the fermentation of sucrose. 1897 was a common year starting on Friday (see link for calendar). ... Eduard Buchner (May 20, 1860 -- August 12, 1917) was a German chemist and zymologist, the winner of the 1907 Nobel Prize in Chemistry for his work on fermentation. ...

3D-Structure

In enzymes, as with other proteins, function is determined by structure. An enzyme can be: A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...

• A monomeric protein, i.e., containing only one polypeptide chain, typically one hundred or more amino acids; or
• an oligomeric protein consisting of several polypeptide chains, different or identical, that act together as a unit.

As with any protein, each monomer is actually produced as a long, linear chain of amino acids, which folds in a particular fashion to produce a three-dimensional product. Individual monomers may then combine via non-covalent interactions to form a multimeric protein. In chemistry, a monomer (from Greek mono one and meros part) is a small molecule that may become chemically bonded to other monomers to form a polymer. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ...

Cartoon showing the active site of an enzyme.

Most enzymes are larger than the substrates they act on and that only a very small portion of the enzyme, around 10 amino acids, come into direct contact with the substrate(s). This region, where binding of the substrate(s) and then the reaction occurs, is known as the active site of the enzyme. Some enzymes contain sites that bind cofactors, which are needed for catalysis. Certain enzymes have binding sites for small molecules, which are often direct or indirect products or substrates of the reaction catalyzed. This binding can serve to increase or decrease the enzyme's activity (depending on the molecule and enzyme), providing a means for feedback regulation. Image File history File links Download high resolution version (1088x713, 80 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (1088x713, 80 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... ... For other uses, including Audio feedback, see Feedback (disambiguation) In cybernetics and control theory, feedback is a process whereby some proportion or in general, function, of the output signal of a system is passed (fed back) to the input. ...

Specificity

Enzymes are usually specific as to the reactions they catalyze and the substrates that are involved in these reactions. Shape, charge complementarity, and hydrophillic/hydrophobic character of enzyme and substrate are responsible for this specificity. In biochemistry, a substrate is a molecule which is acted upon by an enzyme. ...

"Lock and key" model

Enzymes are very specific and it was suggested by Emil Fischer in 1890 that this was because the enzyme had a particular shape into which the substrate(s) fit exactly. This is often referred to as "the lock and key" model. An enzyme combines with its substrate(s) to form a short-lived enzyme-substrate complex. Hermann Emil Fischer (October 9, 1852 - July 15, 1919) was a German chemist and recipient of the Nobel Prize for Chemistry in 1902. ...

Schmatic of Fischer's lock and key model (top) and Koshland's induced fit model (bottom).

Image File history File links LK-IDF.png Summary Lock & Key/Induced Fit Schematic Licensing I, the creator of this work, hereby release it into the public domain. ... Image File history File links LK-IDF.png Summary Lock & Key/Induced Fit Schematic Licensing I, the creator of this work, hereby release it into the public domain. ...

Induced fit model

In 1958 Daniel Koshland suggested a modification to the "lock and key" model. Enzymes are rather flexible structures. The active site of an enzyme could be modified as the substrate interacts with the enzyme. The amino acids sidechains which make up the active site are molded into a precise shape which enables the enzyme to perform its catalytic function. In some cases the substrate molecule changes shape slightly as it enters the active site.

Modifications

Many enzymes contain not only a protein part but need additionally various modifications. These modifications are made posttranslational, i.e., after the polypeptide chain is synthesized. Additional groups can be synthesized onto the polypeptide chain, e.g., phosphorylation or glycosylation of the enzyme. Phosphorylation is the addition of a phosphate (PO4) group to a protein or a small molecule. ... Glycosylation is the process or result of addition of saccharides to proteins and lipids. ...

Another kind of posttranslational modification is the cleavage and splicing of the polypeptide chain. Chymotrypsin, a digestive protease, is produced in inactive form as chymotrypsinogen in the pancreas and transported in this form to the stomach where it is activated. This prevents the enzyme from harmful digestion of the pancreas or other tissue. This type of inactive precursor to an enzyme is known as a zymogen. Chymotrypsin Chymotrypsin (bovine γ chymotrypsin: PDB 1AB9, EC 3. ... Proteases (proteinases, peptidases or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins. ... Chymotrypsinogen is a precursor of the digestive enzyme chymotrypsin (zymogen). ... The pancreas is an organ that serves two functions: exocrine - it produces pancreatic juice containing digestive enzymes. ... The stomach (Gaster) In anatomy, the stomach (in ancient Greek στόμαχος) is an organ in the alimentary canal used to digest food. ... A zymogen is an inactive enzyme precursor. ...

Enzyme cofactors

Some enzymes do not need any additional components to exhibit full activity. However, others require non-protein molecules to be bound for activity. Cofactors can be either inorganic (e.g., metal ions and Iron-sulfur clusters) or organic compounds, which are also known as coenzymes. Inorganic chemistry is the branch of chemistry concerned with the properties and reactions of inorganic compounds. ... An iron-sulfur cluster is a structural motif found in certain metalloproteins, such as the ferredoxins, as well as NADH dehydrogenase and Coenzyme Q - cytochrome c reductase of the electron transfer system. ... An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with exception of carbides, carbonates, carbon oxides and gases containing carbon. ... A coenzyme (a. ...

Enzymes that require a cofactor, but do not have one bound are called apoenzymes. An apoenzyme together with its cofactor(s) constitutes a holoenzyme (i.e, the active form). Most cofactors are not covalently bound to an enzyme, but are closely associated. However, some cofactors known as prosthetic groups are covalently bound (e.g., thiamine pyrophosphate in certain enzymes). An apoenzyme is an enzyme without its cofactor; that is, the protein molecule to which a coenzyme will bind to produce the holoenzyme. ... In biochemistry, holoenzyme may refer either to the complete and operative form of an enzyme with multiple protein subunits or to the combination of an apoenzyme with its cofactor. ... Thiamine mononitrate Thiamine or thiamin, also known as vitamin B1, is a colorless compound with chemical formula C12H17ClN4OS. It is soluble in water and insoluble in alcohol. ...

Most cofactors are either regenerated or chemically unchanged at the end of the reactions. Many cofactors are vitamin-derivatives and serve as carriers to transfer electrons, atoms, or functional groups from an enzyme to a substrate. Common examples are NAD and NADP, which are involved in electron transfer and coenzyme A, which is involved in the transfer of acetyl groups. A Vitamin is an organic molecule required by a living organism in minute amounts for proper health. ... Properties The electron is a fundamental subatomic particle which carries a negative electric charge. ... Properties An atom (Greek άτομον from ά: non and τομον: divisible) is a submicroscopic structure found in all ordinary matter. ... In ecology functional groups are collections of organisms based on morphological, physiological, behavioral, biochemical, or environmental responses or on trophic criteria. ... Nicotinamide adenine dinucleotide (NAD+) (Note that the adenonosyl sugar is of the wrong absolute configuration in the diagram: it should have the same configuration as the nicotinamide sugar. ... Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are two important coenzymes found in cells. ... Acetyl-CoA (CoA with acetate highlighted) Coenzyme A (CoA, CoASH, or HSCoA) is adapted from β-mercaptoethylamine, panthothenate and adenosine triphosphate and used in metabolism in areas such as fatty acid oxidization and the citric acid cycle. ... Acetyl is the radical of acetic acid. ...

Allosteric modulation

Allosteric enzymes change their stucture in response to binding of effectors. Modulation can be direct, where effectors bind directly to binding sites in the enzyme, or indirect, where the effector binds to other proteins or protein subunits that interact with the allosteric enzyme and thus influence catalytic activity. In biochemistry, an enzyme or other protein is allosteric if its activity or efficiency changes in response to the binding of an effector molecule at a so-called allosteric site. ... The EFFector Newsletter is a weekly publication of the Electronic Frontier Foundation (EFF), dedicated to keeping the organization members and subscribers informed of current issues, urging action through Action Alert, and providing a variety of background information and links. ... A binding site is a region on a protein to which specific ligands bind. ... In structural biology, a protein subunit or subunit protein is a single protein molecule that assembles (or coassembles) with other protein molecules to form a multimeric or oligomeric protein. ...

Thermodynamics

Diagram of a catalytic reaction, showing the energy niveau at each stage of the reaction. The substrates usually need a large amount of energy to reach the transition state, which then reacts to form the end product. The enzyme stabilizes the transition state, reducing the energy of the transition state and thus the energy required to get over this barrier.

As with all catalysts, all reactions catalyzed by enzymes must be "spontaneous" (containing a net negative Gibbs free energy). With the enzyme, they run in the same direction as they would without the enzyme, just more quickly. However, the uncatalyzed, "spontaneous" reaction might lead to different products than the catalyzed reaction. Furthermore, enzymes can couple two or more reactions, so that a thermodynamically favorable reaction can be used to "drive" a thermodynamically unfavorable one. For example, the cleavage of the high-energy compound ATP is often used to drive other, energetically unfavorable chemical reactions. Image File history File links Improvement from Image:Activation2. ... Image File history File links Improvement from Image:Activation2. ... In thermodynamics the Gibbs free energy is a thermodynamic potential and is therefore a state function of a thermodynamic system. ... Adenosine 5-triphosphate (ATP) is the nucleotide known in biochemistry as the molecular currency of intracellular energy transfer; that is, ATP is able to store and transport chemical energy within cells. ...

Enzymes catalyze the forward and backward reactions equally. They do not alter the equilibrium itself, but only the speed at which it is reached. Carbonic anhydrase catalyzes its reaction in either direction depending on the conditions. Equilibrium or balance is any of a number of related phenomena in the natural and social sciences. ... Carbonic anhydrase (carbonate dehydratase) is a family of zinc-containing enzymes that catalyze the rapid interconversion of carbon dioxide and water into carbonic acid, protons, and bicarbonate ions. ...

(in tissues - high CO₂ concentration)

(in lungs - low CO₂ concentration)

Biological tissue is a substance made up of cells that perform a similar function. ... The lungs flank the heart and great vessels in the chest cavity. ...

Kinetics

In 1913, Leonor Michaelis and Maud Menten proposed a quantitative theory of enzyme kinetics, which is referred to as Michaelis-Menten kinetics. Their work was futher developed by G. E. Briggs and J. B. S. Haldane, who derived numerous kinetic equations that are still widely used today. Leonor Michaelis (January 16, 1875 – October 8, 1947) was a German biochemist and physician famous for his work with Maud Menten in enzyme kinetics and Michaelis-Menten kinetics. ... Maud Leonora Menten (March 20, 1879 – July 26, 1960) was a Canadian medical scientist who made significant contributions to enzyme kinetics and histochemistry. ... It has been suggested that this article or section be merged with Enzyme. ... Michaelis-Menten kinetics describe the rate of enzyme mediated reactions for many enzymes. ... J.B.S. Haldane with his second wife Helen Spurway John Burdon Sanderson Haldane (November 5, 1892 – December 1, 1964), who normally used J.B.S. as a first name, was a British geneticist and evolutionary biologist. ...

Enzymes can perform up to several million catalytic reactions per second; to determine the maximum speed of an enzymatic reaction, the substrate concentration is increased until a constant rate of product formation is achieved. This is the maximum velocity (V_max) of the enzyme. In this state, all enzyme active sites are saturated with substrate. However, V_max is only one kinetic parameter that biochemists are interested in. The amount of substrate needed to achieve a given rate of reaction is also of interest. This can be expressed by the Michaelis-Menten constant (K_m), which is the substrate concentration required for an enzyme to reach one half its maximum velocity. Each enzyme has a characteristic K_m for a given substrate. Michaelis-Menten kinetics describe the rate of enzyme mediated reactions for many enzymes. ...

The efficiency of an enzyme can be expressed in terms of k_cat/K_m. The quantity k_cat, also called the turnover number, incorporates the rate constants for all steps in the reaction, and is the quotient of V_max and the total enzyme concentration. k_cat/K_m is a useful quantity for comparing different enzymes against each other, or the same enzyme with different substrates, because it takes both affinity and catalytic ability into consideration. The theoretical maximum for k_cat/K_m, called diffusion limit, is about 10⁸ to 10⁹ (M^-1 s^-1). At this point, every collision of the enzyme with its substrate will result in catalysis and the rate of product formation is not limited by the reaction rate but by the diffusion rate. Enzymes that reach this k_cat/K_m value are called catalytically perfect or kinetically perfect. Example of such enzymes are triose-phosphate isomerase, carbonic anhydrase, acetylcholinesterase, catalase, fumarase, ß-lactamase, and superoxide dismutase. (Fig. ... Carbonic anhydrase (carbonate dehydratase) is a family of zinc-containing enzymes that catalyze the rapid interconversion of carbon dioxide and water into carbonic acid, protons, and bicarbonate ions. ... link title Catalase Catalase (human erythrocyte catalase: PDB 1DGF, EC 1. ...

The quantum-mechanical (physical) model of enzyme catalysis explains how certain enzymes work faster than previously thought possible. This is achieved by a process known as tunneling, which allows electron and proton transfers to "tunnel" through activation barriers rather go over them. Fig. ... Quantum tunneling is the quantum-mechanical effect of transitioning through a classically-forbidden energy state. ...

Inhibition

A competitive inhibitor binds reversibly to the enzyme, preventing the binding of substrate. On the other hand, binding of substrate prevents binding of the inhibitor, thus substrate and inhibitor compete for the enzyme.

Diagram showing the mechanism of non-competitive inhibition.

Enzymes reaction rates can be decreased by competitive, non-competitive, partially competitive, uncompetitive inhibition, and mixed inhibition. Drawn by G. Andruk January 31 2005 and released under GNU Free Documentation License. ... Drawn by G. Andruk January 31 2005 and released under GNU Free Documentation License. ... Image File history File links Download high resolution version (820x575, 52 KB) Created by Jerry Crimson Mann 19:04, 1 August 2005 (UTC). ... Image File history File links Download high resolution version (820x575, 52 KB) Created by Jerry Crimson Mann 19:04, 1 August 2005 (UTC). ...

Competitive inhibition

In competitive inhibition, the inhibitor binds to the substrate binding site as shown (right part b), thus preventing substrate binding. Malonate is a competitive inhibitor of the enzyme succinate dehydrogenase, which catalyzes the oxidation of succinate to fumarate. The malonate (also propanedioate) ion is CH2(COO)22- (malonic acid minus two hydrogen ions). ... Succinate is the anion of succinic acid. ... A fumarate is a salt or ester of fumaric acid. ...

Competive inhibition causes the K_m value to increase, but does not effect V_max.

Non-competitive inhibition

Non-competitive inhibitors never bind to the active center, but to other parts of the enzyme that can be far away from the substrate binding site, consequently, there is no competition between the substrate and inhibitor for the enzyme. The extent of inhibition depends entirely on the inhibitor concentration and will not be affected by the substrate concentration. For example, cyanide combines with the copper prosthetic groups of the enzyme cytochrome c oxidase, thus inhibiting cellular respiration. This type of inhibition is typically irreversible, meaning that the enzyme will no longer function. A cyanide is any chemical compound that contains the cyano group C≡N, with the carbon atom triple-bonded to the nitrogen atom. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic brown Atomic mass 63. ... Cytochrome c oxidase The enzyme cytochrome c oxidase (PDB 2OCC, EC 1. ... Cellular respiration is the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. ...

By changing the conformation (the three-dimensional structure) of the enzyme, the inhibitors either disable the ability of the enzyme to bind or turn over its substrate. The enzyme-inhibitor (EI) and enzyme-inhibitor-substrate (EIS) complex have no catalytic activity. In chemistry, a chemical conformation is the spatial arrangement of atoms in a molecule. ...

Non-Competive inhibition causes a decrease in V_max, but does not change the K_m value.

Partially competitive inhibition

The mechanism of partially competitive is similar to that of non-competitive inhibition, except that the EIS-complex has catalytic activity, which may be lower or even higher (partially competitive activation) than that of the enzyme-substrate (ES) complex.

Typically has a lower V_max, but an unaffected K_m value.

Uncompetitive inhibition

Uncompetitive inhibition occurs when the inhibitor binds only to the enzyme-substrate complex, not to the free enzyme, the EIS complex is catalytically inactive. This mode of inhibition is rare.

Uncompetive causes a decrease in V_max and the K_m value.

Mixed inhibition

Mixed inhibitors can bind to both the enzyme and the ES complex. It has the properties of both competitive and uncompetive inhibition.

Both a decrease in V_max and an increase in the the K_m value are seen in mixed inhibition.

Metabolic pathways and allosteric enzymes

Several enzymes can work together in a specific order, creating metabolic pathways. In a metabolic pathway, one enzyme takes the product of another enzyme as a substrate. After the catalytic reaction, the product is then passed on to another enzyme. The end product(s) of such a pathway are often inhibitors for one of the first enzymes of the pathway (usually the first irreversible step, called committed step), thus regulating the amount of end product made by the pathways. Such a regulatory mechanism is called a negative feedback mechanism, because the amount of the end product produced is regulated by its own concentration. Negative feedback mechanism can effectively adjust the rate of synthesis of intermediate metabolites according to the demands of the cells. This helps with effective allocations of materials and energy economy, and it prevents the excess manufacture of end products. Like other homeostatic devices, the control of enzymatic action helps to maintain a stable internal environment in living organisms. In biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell, catalyzed by enzymes, to achieve in either the formation of a metabolic product to be used or stored by the cell, or the initiation of another metabolic pathway (then called a flux generating step). ... An inhibitor is a type of effector that decreases or prevents a chemical reaction. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Homeostasis is the property of an open system, especially living organisms, to regulate its internal environment to maintain a stable, constant condition, by means of multiple dynamic equilibrium adjustments, controlled by interrelated regulation mechanisms. ...

Enzyme naming conventions

By common convention, an enzyme's name consists of a description of what it does, with the word ending in -ase. Examples are alcohol dehydrogenase and DNA polymerase. Kinases are enzymes that transfer phosphate groups. This results in different enzymes with the same function having the same basic name; they are therefore distinguished by other characteristics, such their optimal pH (alkaline phosphatase) or their location (membrane ATPase). Furthermore, the reversibility of chemical reactions means that the normal physiological direction of an enzyme's function may not be that observed under laboratory conditions. This can result in the same enzyme being identified with two different names: one stemming from the formal laboratory identification as described above, the other representing its behavior in the cell. For instance the enzyme formally known as xylitol:NAD+ 2-oxidoreductase (D-xylulose-forming) is more commonly referred to in the cellular physiological sense as D-xylulose reductase, reflecting the fact that the function of the enzyme in the cell is actually the reverse of what is often seen under in vitro conditions. Alcohol Dehydrogenase Alcohol dehydrogenases are a group of dehydrogenase enzymes that occur in many organisms and facilitate the conversion between alcohols and aldehydes or ketones. ... DNA polymerase 3D structure. ... In biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific target molecules (substrates); the process is termed phosphorylation. An enzyme that removes phosphate groups from targets is known as a phosphatase. ... In chemistry, a phosphate is a polyatomic ion or radical consisting of one phosphorus atom and four oxygen. ... The correct title of this article is pH. The initial letter is capitalized due to technical restrictions. ... Alkaline phosphatase, drawn from PDB 1ANI. Alkaline phosphatase (ALP) (EC 3. ... ATPases are a class of enzymes that catalyze the decomposition of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and a free phosphate ion. ...

The International Union of Biochemistry and Molecular Biology has developed a nomenclature for enzymes, the EC numbers; each enzyme is described by a sequence of four numbers, preceded by "EC". The first number broadly classifies the enzyme based on its mechanism: Nomenclature is a system of naming and categorizing objects in a given category. ... EC numbers (Enzyme Commission numbers) are a numerical classification scheme for enzymes, based on the chemical reactions they catalyze. ...

The toplevel classification is

• EC 1 Oxidoreductases: catalyze oxidation/reduction reactions
• EC 2 Transferases: transfer a functional group (e.g. a methyl or phosphate group)
• EC 3 Hydrolases: catalyze the hydrolysis of various bonds
• EC 4 Lyases: cleave various bonds by means other than hydrolysis and oxidation
• EC 5 Isomerases: catalyze isomerization changes within a single molecule
• EC 6 Ligases: join two molecules with covalent bonds

The complete nomenclature can be browsed at http://www.chem.qmul.ac.uk/iubmb/enzyme/ In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule (the oxidant, also called the hydrogen donor or electron donor) to another (the reductant, also called the hydrogen acceptor or electron acceptor). ... The most fundamental reactions in chemistry are the redox processes. ... In biochemistry, a transferase is an enzyme that catalyzes the transfer of a functional group (e. ... In ecology functional groups are collections of organisms based on morphological, physiological, behavioral, biochemical, or environmental responses or on trophic criteria. ... In biochemistry, a hydrolase is an enzyme that can break a chemical bond by hydrolysis. ... Hydrolysis is a chemical process in which a molecule is cleaved into two parts by the addition of a molecule of water. ... In biochemistry, a lyase is an enzyme that breaks various chemical bonds by means other than hydrolysis and oxidation, often forming a new double bond or a new ring structure. ... In biochemistry, an isomerase is any enzyme that catalyses the interconversion of isomers. ... In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently. ... In biochemistry, a ligase is an enzyme that can catalyse the joining of two molecules (ligation or gluing together) by forming a new chemical bond, with accompanying hydrolysis of ATP or other similar molecules. ... Covalently bonded hydrogen and carbon in a molecule of methane. ...

Industrial Applications

Application	Enzymes used	Uses	Notes and examples
Biological detergent	Primarily proteases, produced in an extracellular form from bacteria	Used for presoak conditions and direct liquid applications helping with removal of protein stains from clothes.
	Amylase enzymes	Detergents for machine dishwashing to remove resistant starch residues
Baking industry	Fungal alpha-amylase enzymes: normally inactivates about 50 degrees Celsius, destroyed during baking process	Catalyze breakdown of starch in the flour to sugar. Yeast action on sugar produces carbon dioxide. Used in production of white bread, buns, and rolls	alpha-amylase catalyzes the release sugar monomers from starch
	Protease enzymes	Biscuit manufacturers use them to lower the protein level of flour.
Baby foods	Trypsin	To predigest baby foods
Brewing industry	Enzymes from barley are released during the mashing stage of beer production.	They degrade starch and proteins to produce simple sugar, amino acids and peptides that are used by yeast to enhance fermentation.	Germinating barley used for malt.
	Industrially produced barley enzymes.	Widely used in the brewing process to substitute for the natural enzymes found in barley.
	Amylase, glucanases, proteases	Split polysaccharides and proteins in the malt
	Betaglucosidase	Improve the filtration characteristics.
	Amyloglucosidase	Low-calorie beer
	Proteases	Remove cloudiness during storage of beers.
Fruit juices	Cellulases, pectinases	Clarify fruit juices
Dairy industry	Rennin, derived from the stomachs of young ruminant animals (calves, lambs, kids)	Manufacture of cheese, used to split protein	Note: As animals age rennin production decreases and is replaced by another protease, pepsin, which is not suitable for cheese production. In recent years the increase in cheese consumption, as well as increased beef production, has resulted in a shortage of rennin and escalating prices.
	Microbially produced enzyme	Now finding increasing use in the dairy industry	Roquefort cheese
	Lipases	Is implemented during the production of Roquefort cheese to enhance the ripening of the blue-mould cheese.
	Lactases	Break down lactose to glucose and galactose
Starch industry	Amylases, amyloglucosideases and glucoamylases	Converts starch into glucose and various syrups	Glucose Fructose
	Glucose isomerase	Converts glucose into fructose (high fructose syrups derived from starchy materials have enhanced sweetening properties and lower calorific values)
Rubber industry	Catalase	To generate oxygen from peroxide to convert latex to foam rubber
Paper industry	Amylases	Degrade starch to lower viscosity product needed for sizing and coating paper
Photographic industry	Protease (ficin)	Dissolve gelatin off the scrap film allowing recovery of silver present

A detergent is a compound, or a mixture of compounds, intended to assist cleaning. ... Proteases (proteinases, peptidases or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins. ... Kingdoms/Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Iya Kodie Lovie :D ŴÕŤ Ú ÚÞ ²? lol ow good am i :P iya nat lv :D im not lookin forward to d. ... Image File history File links Download high resolution version (2048x1536, 748 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Wikibooks Cookbook has more about this subject: Baking Baking is the technique of cooking food in an oven by dry heat applied evenly throughout the oven. ... Divisions Chytridiomycota Deuteromycota Zygomycota Glomeromycota Ascomycota Basidiomycota Yellow fungus Fungus growing on a tree in Borneo A fungus (plural fungi) is a eukaryotic organism that digests its food externally and absorbs the nutrient molecules into its cells. ... Look up flour on Wiktionary, the free dictionary. ... Structural formula of amylose File links The following pages link to this file: Amylose Categories: User-created public domain images ... Structural formula of amylose File links The following pages link to this file: Amylose Categories: User-created public domain images ... Baby food is any food that is made specifically for infants, roughly between the ages of six months to two years. ... // Chemistry and Function The enzyme trypsin cleaves proteins at the carboxyl side (or C-terminus) of the basic amino acids lysine and arginine except when these two residues are followed by proline. ... The Brewer, designed and engraved, in the Sixteenth. ... Subject Malted (germinated) barley for Single Malt Scotch in the malting room at the Laphroaig distillery on Islay in Scotland. ... Subject Malted (germinated) barley for Single Malt Scotch in the malting room at the Laphroaig distillery on Islay in Scotland. ... Malted barley Malting is a process applied to cereal grains, in which the grains are made to germinate and then quickly dried before the plant develops. ... A mug of lager beer, showing the golden colour of the beer and the foamy head floating on top. ... Juice can refer to: The liquid naturally contained in plants. ... Dairy farm near Oxford, New York, July 2001 In many northern-hemisphere countries a dairy is a facility for the extraction and processing of animal milk (mostly from cows, sometimes from buffaloes, sheep or goats) for human consumption. ... A ruminant is any hooved animal that digests its food in two steps, first by eating the raw material and regurgitating a semi-digested form known as cud, then eating the cud, a process called ruminating. ... Image File history File links Download high resolution version (1003x800, 106 KB) Roquefort, a type of Protected Designation of Origin cheese made in France. ... Image File history File links Download high resolution version (1003x800, 106 KB) Roquefort, a type of Protected Designation of Origin cheese made in France. ... A lipase is a water-soluble enzyme that catalyzes the hydrolysis of ester bonds in water–insoluble, lipid substrates. ... Roquefort is a flavorful ewes-milk blue cheese from the south of France, and one of the most famous of all French cheeses. ... Danish Blue Throughout the less upmarket areas of shopping and feeding-out, blue cheese almost invariably means Danish Blue. It, by itself, is on the shelf in corner groxceries. ... Starch is a complex carbohydrate which is insoluble in water. ... Inverted sugar syrup is sucrose-based syrup treated with the enzyme invertase, and/or an acid, which splits each sucrose molecule into one glucose and one fructose molecule, giving a more rounded sweetness and preventing crystallization. ... Image File history File links Glucose. ... This image is ineligible for copyright and therefore in the public domain, because it consists entirely of information that is common property and contains no original authorship. ... Glucose (Glc), a monosaccharide, is one of the most important carbohydrates. ... A calorie is a unit of measurement for energy. ... Rubber is an elastic hydrocarbon polymer which occurs as a milky emulsion (known as latex) in the sap of a number of plants but can also be produced synthetically. ... link title Catalase Catalase (human erythrocyte catalase: PDB 1DGF, EC 1. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Peroxide has three distinct meanings: // Colloquial meaning In common usage, peroxide is an aqueous solution of hydrogen peroxide (HOOH or H2O2) sold for use as a disinfectant or mild bleach. ... The extraction of Latex from a tree; Latex is used in Rubber production Latex, as found in nature, is the milky sap of many plants that coagulates on exposure to air. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... α-Amylase Amylase (EC 3. ... The pitch drop experiment at the University of Queensland. ... International Paper Company, on the Sampit River, Georgetown, SC Image taken by me, released under GFDL Pollinator File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Lens and mounting of a large format camera Wikibooks has more about this subject: Photography Photography is the process of making pictures by means of the action of light. ... Gelatin (also gelatine) is a translucent brittle solid substance, colorless or slightly yellow, nearly tasteless and odorless, which is created by prolonged boiling of animal skin and connective tissue. ... Undeveloped Arista black and white film, ISO 125. ... General Name, Symbol, Number silver, Ag, 47 Chemical series transition metals Group, Period, Block 11, 5, d Appearance lustrous white metal Atomic mass 107. ...

See also

• List of enzymes
• Enzyme Kinetics

This article is a list of enzymes, sorted by their respective sub-categories and EC number. ... It has been suggested that this article or section be merged with Enzyme. ...

References

• Koshland D. The Enzymes, v. I, ch. 7, Acad. Press, New York, 1959
• Perutz M. Proc. Roy. Soc., B (1967) 167, 448,
• Cha, Y., Murray, C. J. & Klinman, J. P. Science (1989) 243, 1325-1330 .
• Leonor Michaelis and Maud Menten, Die Kinetik der Invertinwirkung, Biochem. Z. (1913) 49, 333-369.
• G. E. Briggs and J. B. S. Haldane, A note on the kinetics of enzyme action, Biochem. J., (1925) 19, 339-339.
• M.V. Volkenshtein, R.R. Dogonadze, A.K. Madumarov, Z.D. Urushadze, Yu.I. Kharkats. Theory of Enzyme Catalysis.- Molekuliarnaya Biologia, (1972), 431-439 (In Russian, English summary)

Leonor Michaelis (January 16, 1875 – October 8, 1947) was a German biochemist and physician famous for his work with Maud Menten in enzyme kinetics and Michaelis-Menten kinetics. ... Maud Leonora Menten (March 20, 1879 – July 26, 1960) was a Canadian medical scientist who made significant contributions to enzyme kinetics and histochemistry. ... J.B.S. Haldane with his second wife Helen Spurway John Burdon Sanderson Haldane (November 5, 1892 – December 1, 1964), who normally used J.B.S. as a first name, was a British geneticist and evolutionary biologist. ... Revaz Dogonadze Revaz Dogonadze (November 21, 1931 - May 13, 1985) was a notable Georgian scientist, one of the founders of quantum electrochemistry, main author of the Quantum-Mechanical Theory of Kinetics of the Elementary Act of Chemical, Electrochemical and Biochemical Processes in Polar Liquids, Corresponding Member of the Georgian Academy...

External links

Wikimedia Commons has media related to:

Enzyme

• ExPASy enzyme database, links to Swiss-Prot sequence data, entries in other databases and to related literature searches
• PDBsum links to the known 3-D structure data of enzymes in the Protein Data Bank
• BRENDA, comprehensive compilation of information and literature references about all known enzymes; requires payment by commercial users
• Weizmann Institute's Genecards Database, extensive database of protein properties and their associated genes.
• Cytochrome P450 enzymes site lists over 4000 versions of enzymes from this cytochrome in plants and animals

Image File history File links Commons-logo. ... The Wikimedia Commons (also called Commons or Wikicommons) is a repository of free content images, sound and other multimedia files. ... Swiss-Prot is a curated biological database of protein sequences created in 1986 by Amos Bairoch during his PhD and developed by the Swiss Institute of Bioinformatics and the European Bioinformatics Institute. ... The Protein Data Bank (PDB) is a repository for 3-D structural data of proteins and nucleic acids. ...