Cysteine Image File history File links Download high resolution version (1267x1288, 21 KB) Licensing File links The following pages link to this file: Amino acid Cysteine User:Benjah-bmm27/Gallery ... Image File history File links Download high resolution version (694x740, 24 KB) Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Cysteine User:Benjah-bmm27/Gallery Cysteine (data page) ... Image File history File links Size of this preview: 534 × 600 pixelsFull resolution (979 × 1100 pixel, file size: 240 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Cysteine ...
Systematic (IUPAC) name
(2R)-2-amino-3-sulfanyl-propanoic acid
Identifiers
CAS number	52-90-4
PubChem	5862
Chemical data
Formula	C3H7NO2S
Mol. weight	121.16
SMILES	N[C@@H](S)C(O)=O
Complete data

Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. Cysteine is unique amongst the twenty natural amino acids as it contains a thiol group. Thiol groups can undergo oxidation/reduction (redox) reactions; when cysteine is oxidised it can form cystine, which is two cysteine residues joined by a disulfide bond. This reaction is reversible: as reduction of this disulphide bond regenerates two cysteine molecules. The disulphide bonds of cystine are crucial to defining the structures of many proteins. IUPAC nomenclature is a systematic way of naming organic chemical compounds. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences and alloys. ... PubChem is a database of chemical molecules. ... This article does not cite its references or sources. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Standard atomic weight 12. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Standard atomic weight 32. ... The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... The simplified molecular input line entry specification or SMILES is a specification for unambiguously describing the structure of chemical molecules using short ASCII strings. ... Physical properties Hazard properties Flash point - N/A R/S statement R: N/A S: N/A RTECS number: N/A Chemical properties Pharmacological properties OrganicBox_complete References a  [1] This article is maintained by WP:Chemicals (Talk)  WP:Drugs (Talk)  WP:Molecular and Cellular Biology (Talk)   Categories: ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Standard atomic weight 32. ... Phenylalanine is one of the standard amino acids. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... This list of standard proteinogenic amino acids details the chemical structures and properties of the twenty standard amino acids used in proteins by living cells. ... Sulphydryl // In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom (-SH). ... Illustration of a redox reaction Redox (shorthand for oxidation/reduction reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... The most fundamental reactions in chemistry are the redox processes. ... Chemical structure of cystine formed from L-cysteine (under biological conditions) 3D representation of cystine with the disulfide bond shown in yellow Cystine is a conditionally non-essential crystalline, sulfur-containing amino acid. ... In chemistry, a disulfide bond is a single covalent bond derived from the coupling of thiol groups. ...

Cysteine is often involved in electron-transfer reactions as it is easily oxidized. Cysteine is also part of the antioxidant glutathione. Illustration of a redox reaction Redox (shorthand for oxidation/reduction reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... Skeletal formula of glutathione 3D model of glutathione Glutathione (GSH), whose IUPAC name is 2-amino-5-{[2-[(carboxymethyl)amino]- 1-(mercaptomethyl)-2-oxoethyl]amino}-5-oxopentanoic acid, is γ-glutamylcysteinylglycine, a tripeptide. ...

N-acetyl-L-cysteine (NAC) is a form of cysteine where an acetyl group is attached to cysteine's nitrogen atom and is sold as a dietary supplement. Cysteine is named after cystine, which comes from the Greek word kustis meaning bladder − cystine was first isolated from kidney stones. NAC is an acronym that can stand for: N-acetylcysteine Net Access Corporation, a/k/a NAC.NET National Action Committee on the Status of Women, Canada National Administrative Council National Airways Corporation, New Zealand National Agency Check National Aquatic Centre, Dublin, Ireland National Automotive Center National Arts Centre, Ottawa... Acetyl is the radical of acetic acid. ... In anatomy, the urinary bladder is a hollow, muscular, and distensible (or elastic) organ that sits on the pelvic floor in mammals. ... Kidney stones, or Renal calculi, are solid concretions (crystal aggregations) of dissolved minerals in urine; calculi typically form inside the kidneys or ureters. ...

Reactions

As cysteine contains a sulphydryl group, it can undergo redox reactions. Oxidation of cysteine can produce a disulfide bond with another thiol, or further oxidation can produce sulphfinic or sulfonic acids. Sulphydryl // In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom (-SH). ... Illustration of a redox reaction Redox (shorthand for oxidation/reduction reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... In chemistry, a disulfide bond is a single covalent bond derived from the coupling of thiol groups. ... It has been suggested that Sulfonic acid/Temp be merged into this article or section. ...

The cysteine thiol group is also a nucleophile and can undergo addition and substitution reactions. Thiol groups become much more reactive when they are ionised, and cysteine residues in proteins have pK_a values close to neutrality, so are often in their reactive thiolate form in the cell.^[1] In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ... In organic chemistry, a nucleophilic addition reaction is an addition reaction where in a chemical compound a pi bond is removed by the creation of two new covalent bonds by the addition of a nucleophile. ... In chemistry, nucleophilic substitution is a class of substitution reaction in which an electron-rich nucleophile attacks a molecule and replaces a group or atom, called the leaving group. ... The acid dissociation constant (Ka), also known as the acidity constant or the acid-ionization constant, is a specific equilibrium constant for the reaction of an acid with its conjugate base in aqueous solution [1]. // When an acid dissolves in water, it partly dissociates forming hydronium ions and its conjugate... In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom (-SH). ...

The thiol group also has a high affinity for heavy metals and proteins containing cysteine will bind metals such as mercury, lead and cadmium tightly.^[2] Look up affinity in Wiktionary, the free dictionary. ... A heavy metal is any of a number of higher atomic weight elements, which has the properties of a metallic substance at room temperature. ... Chelation (from Greek χηλή, chelè, meaning claw) is the process of reversible binding (complexation) of a ligand - the chelant, chelator, chelating agent, sequestering agent, or complexing agent - to a metal ion, forming a metal complex, the chelate. ...

Biological functions

Due to this ability to undergo redox reactions, cysteine has antioxidant properties. Cysteine is an important source of sulfur in human metabolism, and although it is classified as a non-essential amino acid, cysteine may be essential for infants, the elderly, and individuals with certain metabolic disease or who suffer from malabsorption syndromes. Space-filling model of the antioxidant metabolite glutathione. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Standard atomic weight 32. ... A few of the metabolic pathways in a cell. ... An essential amino acid for an organism is an amino acid that cannot be synthesized by the organism from other available resources, and therefore must be supplied as part of its diet. ... Malabsorption is the state of impaired absorption of nutrients in the small intestine. ... In medicine, the term syndrome is the association of several clinically recognizable features, signs, symptoms, phenomena or characteristics which often occur together, so that the presence of one feature alerts the physician to the presence of the others. ...

Cysteine is an important precursor in the production of glutathione in the body and other organisms. The systemic availability of oral glutathione (GSH) is negligible; the vast majority of it must be manufactured intracellularly. Glutathione is a tripeptide antioxidant made up of the three amino acids cysteine, glycine and glutamate. Glutamate and glycine are readily available in most North American diets, but the availability of cysteine makes it be the rate-limiting substrate for the synthesis of glutathione within the cell. It is the sulfhydryl (thiol) group (SH) of cysteine that serves as proton-donor and is responsible for the biological activity of glutathione.^[3] A protein precursor is an inactive protein (or peptide) that can be turned into an active form by posttranslational modification. ... A tripeptide is a peptide consisting of three amino acids, e. ... For the plant, see Glycine (plant). ... Glutamate is the anion of glutamic acid. ... In biochemistry, a substrate is a molecule upon which an enzyme acts. ... In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ...

The free amino acid cysteine (supplied supplementally by NAC) does not represent an ideal delivery system to the cell. Cysteine is potentially toxic and is spontaneously catabolized in the gastrointestinal tract and blood plasma. Conversely, cysteine absorbed during digestion as cystine (two cysteine molecules linked by a disulfide bond) in the gastrointestinal tract is more stable than the free amino acid cysteine. Cystine travels safely through the GI tract and blood plasma and is promptly reduced to the two cysteine molecules upon cell entry.^[3] N-acetylcysteine is a chemical, commonly called NAC, produced by the body that enhances the production of the co-enzyme glutathione, a powerful antioxidant. ... ... Chemical structure of cystine formed from L-cysteine (under biological conditions) 3D representation of cystine with the disulfide bond shown in yellow Cystine is a conditionally non-essential crystalline, sulfur-containing amino acid. ... Blood plasma is the liquid component of blood, in which the blood cells are suspended. ...

Biochemistry

Cysteine contains a thiol group, which can display nucleophilicity. Some important cysteine-derived nucleophiles include ubiquitin ligases, which transfer ubiquitin to its pendant proteins, and caspases, which engage in proteolysis in the apoptotic cycle. Inteins often function with the help of a catalytic cysteine. These roles are typically limited to the intracellular milieu, where the environment is reducing, and cysteine is not oxidized to cystine. In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ... Ubiquitin is a very conserved small regulatory protein that is ubiquitous in eukaryotes. ... In biochemistry, a ligase is an enzyme that can catalyse the joining of two molecules (ligation or glue together) by forming a new chemical bond, with concomitant hydrolysis of ATP or other similar molecules. ... Caspases are a group of cysteine proteases, enzymes with a crucial cysteine residue that can cleave other proteins, after an aspartic acid residue, a specificity which is unusual among proteases. ... An intein is a segment of a protein that is able to excise itself and rejoin the remaining portions (the exteins) with a peptide bond. ...

Cysteines play a valuable role by crosslinking proteins. This increases the molecular stability in the harsh extracellular environment, and also functions to confer proteolytic resistance (since protein export is a costly process, minimizing its necessity is advantageous). Intracellularly, disulfide bridges between cysteines within a polypeptide support the protein's secondary structure. Insulin is an example of a protein with cystine crosslinking, where two separate peptide chains are connected by a pair of disulfide bonds. Insulin (from Latin insula, island, as it is produced in the Islets of Langerhans in the pancreas) is a polypeptide hormone that regulates carbohydrate metabolism. ...

Protein Disulfide Isomerases catalyze the proper formation of disulfide bonds; the cell transfers dehydroascorbic acid to the endoplasmic reticulum which oxidises the environment. In this environment, cysteines are generally oxidized to cystine and no longer functions as a nucleophile. Protein disulfide isomerase or PDI (EC 5. ... A disulfide bond (SS-bond), also called a disulfide bridge, is a strong covalent bond between two sulfhydryl groups. ... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ...

Dietary sources

Cysteine can be found in eggs, meat, red peppers, garlic, onions, broccoli, brussel sprouts, oats, milk, whey protein, and wheat germ. However, it is not classified as an essential amino acid, and can usually be synthesized by the human body under normal physiological conditions if a sufficient quantity of methionine is available. An essential amino acid or indispensable amino acid, is an amino acid that cannot be synthesized de novo by the organism (usually referring to humans), and therefore must be supplied in the diet. ... Methionine (Met, M. C5H11NO2S) is an essential nonpolar amino acid, and a lipotropic. ...

Production

Currently the cheapest source of material from which food grade L-cysteine may be purified in high yield is by hydrolysis of molecules in human hair. Other sources include feathers and pig bristles. The companies producing cysteine by hydrolysis are located mainly in China. There is some debate whether or not consuming L-cysteine derived from human hair constitutes cannibalism. Although many other amino acids were accessible via fermentation for some years, L-Cysteine was unavailable until 2001 when a German company introduced a production route via fermentation (non-human, non-animal origin.) Cysteine is a naturally occurring hydrophobic amino acid which has a sulfhydryl group and is found in most proteins, however only in small quantities. ... Hydrolysis is a chemical reaction or process in which a chemical compound reacts with water. ... Long braided hair Hair is the filamentous outgrowth of the epidermis found in mammals. ... This article is about consuming ones own species. ... This article or section does not cite any references or sources. ...

A source of bonded cysteine (cystine) is undenatured bovine whey protein; this is the same form as that in human breast milk. Percentages are relative to US recommendations for adults. ...

Applications

Cysteine (mostly in the naturally occurring form L-cysteine) is used for applications in the food, pharmaceutical and personal care industries. One of the largest applications is the production of various flavors. For example, reacting cysteine with sugars in a Maillard reaction yields meat flavors. L-cysteine is also used as a processing aid for baking. Small quantities (in the tens of ppm range) help to soften the dough and thus reduce processing time. The Maillard reaction is a chemical reaction between an amino acid and a reducing sugar, usually requiring the addition of heat. ... Flour treatment agents (also called improving agents) are food additives added to flour in order to improve its properties. ...

The cysteine derivative N-acetyl cysteine (NAC) is often used as a cough medicine as it breaks up the disulfide bonds in the mucus and thus liquefies it, making it easier to cough up. NAC is also used as a dietary supplement as already indicated above, as well as a specific antidote in cases of acetominophen overdose. Acetylcysteine (rINN) (IPA: ), also known as N-acetylcysteine (abbreviated NAC), is a pharmacological agent used mainly as a mucolytic and in the management of paracetamol overdose. ... Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). ... An antidote is a substance which can counteract a form of poisoning. ... Acetaminophen (USAN) or paracetamol (INN), is a popular analgesic and antipyretic drug that is used for the relief of fever, headaches, and other minor aches and pains. ...

In the field of personal care, cysteine is used for permanent wave applications predominantly in Asia. Again the cysteine is used for breaking up the disulfide bonds in the hair's keratin. Turn of the century advertisement for Nesslers permanent wave machine. ... A strand of human hair under magnification Hair is also the name of a musical, see respective articles for the stage production and the movie. ... Microscopy of keratin filaments inside cells. ...

Cysteine is a very popular target for site-directed labeling experiments to investigate biomolecular structure and dynamics. Maleimides will selectively attach to cysteine using a covalent michael-addition. Site-directed spin labeling for EPR also uses cysteine extensively. Maleimides are a group of organic compounds with a 2,5-pyrroledione skeleton. ... // Introduction Site-directed spin labeling technique is a tool for investigating protein local dynamics using electron spin resonance. ...

In his 2006 doctoral thesis Ville Salaspuro proposes that:

The elevated aerodigestive tract cancer risk observed in smokers and drinkers may be the result of the increased acetaldehyde exposure. Acetaldehyde produced in the oral cavity during ethanol challenge was significantly decreased by a buccal L-cysteine -releasing tablet. Also smoking-derived acetaldehyde could be totally removed by using a tablet containing L-cysteine.

In a 1994 report released by five top cigarette companies, cysteine is one of the 599 additives to cigarettes. Its use or purpose, however, is unknown, like most cigarette additives.^[4] Its inclusion in cigarettes could offer two benefits: Acting as an expectorant, since smoking increases mucus production in the lungs; and increasing the beneficial antioxidant glutathione (which is diminished in smokers). A smoking symbol. ... A cough medicine or antitussive is a medication given to people to help them stop coughing. ... Skeletal formula of glutathione 3D model of glutathione Glutathione (GSH), whose IUPAC name is 2-amino-5-{[2-[(carboxymethyl)amino]- 1-(mercaptomethyl)-2-oxoethyl]amino}-5-oxopentanoic acid, is γ-glutamylcysteinylglycine, a tripeptide. ...

Sheep

Cystine, showing disulfide bond

Cysteine is required by sheep in order to produce wool, however it is an essential amino-acid that cannot be synthesised by the sheep and must be taken in as food from grass. This means that during drought conditions sheep stop producing wool; however, transgenic sheep have been developed which can make their own cysteine. A little concentration of cysteine is used to break the disulfide bonds during the solublisation of recombinant protein preparation. Image File history File links Download high resolution version (1897x2415, 42 KB) Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Cysteine Cystine ... Image File history File links Download high resolution version (1897x2415, 42 KB) Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Cysteine Cystine ... Chemical structure of cystine formed from L-cysteine (under biological conditions) 3D representation of cystine with the disulfide bond shown in yellow Cystine is a conditionally non-essential crystalline, sulfur-containing amino acid. ... In chemistry, a disulfide bond is a single covalent bond derived from the coupling of thiol groups. ... Species See text. ... A genetically modified organism is an organism whose genetic material has been deliberately altered. ...

Hangover Remedy

Cysteine has been linked to aiding in the remedy of certain hangover symptoms. It directly counteracts the poisonous effects of acetaldehyde, a particularly toxic by-product of alcohol in the human body. Cysteine attracts the toxin, breaking it down into the non-toxic acetate, a substance similar to vinegar. The actual effectiveness of consuming cysteine as part of a hangover remedy is unclear.^[5] A hangover (veisalgia) describes the sum of unpleasant physiological effects following heavy consumption of alcoholic beverages. ... R-phrases , , S-phrases , , , Flash point −39 °C Autoignition temperature 185 °C RTECS number AB1925000 Supplementary data page Structure and properties n, εr, etc. ... Acetate, or ethanoate, is the anion of a salt or ester of acetic acid. ...

See also

• selenocysteine
• amino acids
• thiols
• cysteine metabolism
• cystinuria

Skeletal formula of L-selenocysteine Space-filling model of L-selenocysteine Selenocysteine is an amino acid that is present in several enzymes (for example glutathione peroxidases, tetraiodothyronine 5 deiodinases, thioredoxin reductases, formate dehydrogenases, glycine reductases and some hydrogenases). ... Phenylalanine is one of the standard amino acids. ... Sulphydryl // In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom (-SH). ... Cysteine metabolism is comprised of the biological pathways that consume or create cysteine. ... Ë Cystinuria is an inherited autosomal recessive disorder and is characterized by the formation of cystine stones in the kidneys, ureter, and bladder. ...

References

1. ^ Bulaj G, Kortemme T, Goldenberg D (1998). "Ionization-reactivity relationships for cysteine thiols in polypeptides.". Biochemistry 37 (25): 8965-72. PMID 9636038. 
2. ^ Baker D, Czarnecki-Maulden G (1987). "Pharmacologic role of cysteine in ameliorating or exacerbating mineral toxicities.". J Nutr 117 (6): 1003-10. PMID 3298579. 
3. ^ ^{a b} (1)
4. ^ http://quitsmoking.about.com/cs/nicotineinhaler/a/cigingredients.htm
5. ^ http://www.lef.org/protocols/prtcl-004.shtml

External links

• Computational Chemistry Wiki
• International Kidney Stone Institute
• http://www.chemie.fu-berlin.de/chemistry/bio/aminoacid/cystein en.html
• On the hydrophobic nature of cysteine.
• Interaction of alcohol and smoking in the pathogenesis of upper digestive tract cancers - possible chemoprevention with cysteine
• Cystine Kidney Stones
• Links to external chemical sources