In biochemistry, a transaminase or an aminotransferase is an enzyme that catalyzes a type of reaction between an amino acid and an α-keto acid. Specifically, this reaction (transamination) involves removing the amino group from the amino acid, leaving behind an α-keto acid, and transferring it to the reactant α-keto acid and converting it into an amino acid. The enzymes are important in the production of various amino acids, and measuring the concentrations of various transaminases in the blood is important in the diagnosing and tracking many diseases. Biochemistry is the chemistry of life, a bridge between biology and chemistry that studies how complex chemical reactions give rise to life. ... Jump to: navigation, search Ribbon diagram of the catalytically perfect enzyme TIM. Factor D enzyme crystal prevents the immune system from inappropriately running out of control. ... In chemistry and biology, catalysis (in Greek meaning to annul) is the acceleration of the rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... Jump to: navigation, search In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... Transamination is the reaction between an amino acid and an alpha-keto acid. ... In chemistry, especially in organic chemistry and biochemistry, an amino group is an ammonia-like functional group. ... Jump to: navigation, search Concentration is a very common concept used in chemistry and related fields. ... Jump to: navigation, search A disease is any abnormal condition of the body or mind that causes discomfort, dysfunction, or distress to the person affected or those in contact with the person. ...

Mechanism

The coenzyme pyridoxal phosphate (PLP, the coenzyme form of pyridoxine or vitamin B₆) is essential to the transamination reaction. The group is covalently bound to the enzyme and during the reaction is reversibly bound to the reactants. The reaction takes place in two steps: first, the amino acid becomes covalently bound to PLP via its amino group, forming a Schiff base. The PLP–amino acid complex is released from the enzyme. After formation of a carbanion stabilized by the conjugated ring, the product is released as the corresponding α-keto acid. The amino group stays behind attached to PLP, now pyridoxamine phosphate. For the second part of the reaction, this species bonds to an α-keto acid, and in the reverse process, the enzyme binds to the complex. The amino group is transferred, generating a new amino acid and regenerating PLP. This type of reaction is known as a "Ping-Pong reaction". A coenzyme (a. ... Pyridoxal-phosphate (PLP, pyridoxal-5-phosphate) is a cofactor of many enzymatic reactions. ... The two major forms of vitamin B6 are pyridoxine and pyridoxamine. ... The two major forms of vitamin B6 are pyridoxine and pyridoxamine. ... A Schiff base is a functional group or type of chemical compound containing a carbon-nitrogen double bond with the nitrogen atom connected to a aryl group . ... Jump to: navigation, search The two major forms of vitamin B6 are pyridoxine and pyridoxamine. ...

While all enzymes catalyze the "forward" and "reverse" reactions, the transamination reaction is quite reversible as the equilibrium constant K is near 1.0 (that is, the Gibbs free energy ΔG° ≈ 0 kJ/mol). The direction the reactions go in cells depends on the relative concentrations of the amino and α-keto acids. In chemistry, the equilibrium constant is a theoretically-calculated number associated to a reaction which is an useful tool to determine the concentration of various reactants or products in a system where chemical equilibrium occurs. ... Jump to: navigation, search In thermodynamics the Gibbs free energy is a state function of any system defined as G = H − T·S where G is the Gibbs free energy, measured in joules H is the enthalpy, measured in joules T is the temperature, measured in kelvins S is the...

Biochemical function

The transaminases are involved in supplying amino groups for the biosynthesis of several amino acids. Most forms involve glutamate/α-ketoglutarate as one of the species. One use in mammals is ornithine δ-aminotransferase. This enzyme is involved in converting proline, which is synthesized from glutamate, to ornithine (which has two amino groups); ornithine can then be converted to arginine. Another is phosphoserine aminotransferase in the production of serine from 3-phosphoglycerate; this can then be converted to glycine. Plants and bacteria have additional enzymes and pathways to synthesize amino acids that humans and other mammals cannot. Glutamate is the anion of glutamic acid. ... Jump to: navigation, search Orders Subclass Multituberculata (extinct) Plagiaulacida Cimolodonta Subclass Palaeoryctoides (extinct) Subclass Triconodonta (extinct) Subclass Placentalia Afrosoricida Artiodactyla Carnivora Cetacea Chiroptera Creodonta (extinct) Dermoptera Desmostylia (extinct) Embrithopoda (extinct) Hyracoidea Insectivora Lagomorpha Litopterna (extinct) Macroscelidea Notoungulata (extinct) Perissodactyla Pholidota Primates Proboscidea Rodentia Scandentia Sirenia Tubulidentata Xenarthra Subclass Marsupialia Dasyuromorphia... L-Proline is one of the twenty amino acids (formerly, proline was misleadingly called an imino acid) that are used by living organisms as a building block of proteins (so called proteinogenic amino acids). ... Ornithine is an amino acid, whose structure is: NH2-CH2-CH2-CH2-CHNH2-COOH Ornithine is one of the products of the action of the enzyme arginase on L-arginine, creating urea. ... Arginine is one of the 20 most common natural amino acids. ... Serine is one of the 20 natural amino acids. ... Jump to: navigation, search Glycine (Gly, G) is a nonpolar amino acid. ... Jump to: navigation, search Divisions Land plants (embryophytes) Non-vascular plants (bryophytes) Hepaticophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants... 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 Bacteria (singular, bacterium) are a major group of living organisms. ...

In addition, the transaminases have a major role in amino acid catabolism (breakdown), for instance so that the resulting α-keto acid can be converted to a carbohydrate for fuel or structure. If the amino groups were simply removed, they would exist in the blood as ammonia (actually the ammonium form at blood pH), and the high ammonia levels would cause brain damage and eventually death. Instead, transaminases in the liver transfer the amino group from the amino acid to α-ketoglutarate. This leaves behind the α-keto acid, which can be used for various purposes, and the α-ketoglutarate is converted to the amino acid glutamate. Glutamate then undergoes some reactions and feeds the amino groups into the urea cycle, in which they become part of urea that is excreted in the urine. Anabolism is the aspect of metabolism that contributes to growth. ... Jump to: navigation, search Carbohydrates (literally hydrates of carbon) are chemical compounds that act as the primary biological means of storing or consuming energy, other forms being fat and protein. ... Jump to: navigation, search Ammonia is a compound of nitrogen and hydrogen with the formula NH3. ... Fumes from hydrochloric acid and ammonia forming a white cloud of ammonium chloride The Ammonium cation is a positively charged polyatomic ion of the chemical formula NH4+ and a molecular mass of 18. ... The title of this article begins with a capital letter, due to technical limitations of the MediaWiki software. ... The Urea Cycle is a cycle of biochemical reactions occurring in many animal organisms that produces urea from ammonia. ... Urea is an organic compound of carbon, nitrogen, oxygen and hydrogen, with the formula CON2H4 or (NH2)2CO and the structure shown right: Urea is also known as carbamide, especially in the recommended International Non-proprietary Names (rINN) in use in Europe. ... Urine is liquid waste excreted by the kidneys and eventually expelled from the body in a process known as urination. ...

Diagnostic use

The biochemical hub of the body, the liver, has a variety of transaminases to synthesize and break down amino acids and to interconvert energy storage molecules. The concentrations of these in the serum (the non-cellular portion of blood) are normally low. However, if the liver is damaged, the hepatocyte cell membrane becomes more permeable and some of the enzymes leak out into the blood stream. The two transaminases commonly measured are alanine transaminase (ALT) and aspartate transaminase (AST). These levels previously were called the serum glutamate-pyruvate transaminase (SGPT) and the serum glutamate-oxaloacetate transaminase (SGOT). Elevated levels are quite sensitive for liver injury, meaning that they are likely to be present if there is injury. However, they may also be elevated in other conditions. ALT is not commonly found outside the liver; AST too is most commonly found in the liver, but also in significant amounts in cardiac (heart) and skeletal muscle. In fact, measurement of these used to be part of diagnosing heart attacks, although newer enzymes and proteins that are more specific for cardiac damage have largely replaced this usage. Jump to: navigation, search The liver is an organ in vertebrates, including humans. ... Blood plasma is a component of blood. ... Hepatocytes make up 60-80% of the cytoplasmic mass of the liver. ... Jump to: navigation, search Drawing of a cell membrane A component of every biological cell, the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... Alanine transaminase or ALT is an enzyme (EC 2. ... Aspartate transaminase (AST) also called Serum Glutamic Oxaloacetic Transaminase (SGOT) or aspartate aminotransferase (ASAT) (EC 2. ... The sensitivity of a binary classification test or algorithm, such as a blood test to determine if a person has a certain disease, or an automated system to detect faulty products in a factory, is a parameter that expresses something about the tests performance. ... Cardiac muscle is a type of striated muscle found within the heart. ... A top-down view of skeletal muscle Skeletal muscle is a type of striated muscle, attached to the skeleton. ... A myocardial infarction occurs when an atherosclerotic plaque slowly builds up in the inner lining of a coronary artery and then suddenly ruptures, totally occluding the artery and preventing blood flow downstream. ...

In general, any damage to the liver will cause medium elevations in these transaminases (usually called liver enzymes, though of course they are not the only enzymes in the liver). And diagnosis requires synthesis of many pieces of information, including the patient's history, physical examination, and possibly imaging or other laboratory examinations. However, very high elevations of the transaminases suggests severe liver damage, such as viral hepatitis, liver injury from lack of blood flow, or injury from drugs or toxins. Most disease processes cause ALT to rise higher than AST; AST levels double or triple that of ALT are consistent with alcoholic liver disease. In medicine (gastroenterology), hepatitis is any disease featuring inflammation of the liver. ...

References

• Ghany, Marc & Hoofnagle, Jay H. (2005). Approach to the Patient With Liver Disease. In Dennis L. Kasper, Anthony S. Fauci, Dan L. Longo, Eugene Braunwald, Stephen L. Hauser, & J. Larry Jameson (Eds.), Harrison's Principles of Internal Medicine (16th Edition), pp. 1814–1815. New York: McGraw-Hill.
• Nelson, David L. & Cox, Michael M. (2000). Lehninger Principles of Biochemistry (3rd ed.), pp. 628–631, 634, 828–830. New York: Worth Publishers.