Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula HO2CCH(NH2)CH2SH. The thiol side chain in cysteine often participates in enzymatic reactions, as a nucleophile. The thiol is susceptible to oxidation to give the disulfide derivative cystine, which serves an important structural role in many proteins. When used as a food additive, it has the E number E920. It is encoded by the codons UGU and UGC.
Methionine is an essential amino acid in humans. As the substrate for other amino acids such as cysteine and taurine, versatile compounds such as SAM-e, and the important antioxidant glutathione, methionine plays a critical role in the metabolism and health of many species, including humans. It is encoded by the codon AUG.
Taurine, or 2-aminoethanesulfonic acid, is an organic compound that is widely distributed in animal tissues. It is a major constituent of bile and can be found in the large intestine, and accounts for up to 0.1% of total human body weight. Taurine is named after the Latin taurus which means bull or ox, as it was first isolated from ox bile in 1827 by German scientists Friedrich Tiedemann and Leopold Gmelin. It was discovered in human bile in 1846 by Edmund Ronalds.
A thiol or thiol derivative is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The –SH functional group itself is referred to as either a thiol group or a sulfanyl group. Thiols are the sulfur analogue of alcohols, and the word is a portmanteau of "thio-" + "alcohol", with the first word deriving from Greek θεῖον (theion) meaning "sulfur".
Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined together to form macromolecules. This process often consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is usually synonymous with anabolism.
Cysteine dioxygenase (CDO) is a non-heme iron enzyme that catalyzes the conversion of L-cysteine to cysteine sulfinic acid. CDO plays an important role in cysteine catabolism, regulating intracellular levels of cysteine and responding changes in cysteine availability. As such, CDO is highly regulated and undergoes large changes in concentration and efficiency. It oxidizes cysteine to the corresponding sulfinic acid by activation of dioxygen, although the exact mechanism of the reaction is still unclear. In addition to being found in mammals, CDO also exists in some yeast and bacteria, although the exact function is still unknown. CDO has been implicated in various neurodegenerative diseases and cancers, which is likely related to cysteine toxicity.
A sulfonic acid (or sulphonic acid) refers to a member of the class of organosulfur compounds with the general formula R−S(=O)2−OH, where R is an organic alkyl or aryl group and the S(=O)2(OH) group a sulfonyl hydroxide. As a substituent, it is known as a sulfo group. A sulfonic acid can be thought of as sulfuric acid with one hydroxyl group replaced by an organic substituent. The parent compound (with the organic substituent replaced by hydrogen) is the parent sulfonic acid, HS(=O)2(OH), a tautomer of sulfurous acid, S(=O)(OH)2. Salts or esters of sulfonic acids are called sulfonates.
Sulfinic acids are oxoacids of sulfur with the structure RSO(OH). In these organosulfur compounds, sulfur is pyramidal.
A sulfenic acid is an organosulfur compound and oxoacid with the general formula RSOH. It is the first member of the family of organosulfur oxoacids, which also include sulfinic acids and sulfonic acids, RSO2H and RSO3H, respectively. The base member of the sulfenic acid series with R = H is hydrogen thioperoxide.
Peroxiredoxins are a ubiquitous family of antioxidant enzymes that also control cytokine-induced peroxide levels and thereby mediate signal transduction in mammalian cells. The family members in humans are PRDX1, PRDX2, PRDX3, PRDX4, PRDX5, and PRDX6. The physiological importance of peroxiredoxins is illustrated by their relative abundance.
Cystamine (2,2'-dithiobisethanamine) is an organic disulfide. It is formed when cystine is heated, the result of decarboxylation. Cystamine is an unstable liquid and is generally handled as the dihydrochloride salt, C4H12N2S2·2HCl, which is stable to 203-214 °C at which point it decomposes. Cystamine is toxic if swallowed or inhaled and potentially harmful by contact.
Cystathionine is an intermediate in the synthesis of cysteine.
In enzymology, a hypotaurine dehydrogenase (EC 1.8.1.3) is an enzyme that catalyzes the chemical reaction
In enzymology, a sulfinoalanine decarboxylase (EC 4.1.1.29) is an enzyme that catalyzes the chemical reaction
In enzymology, a bile acid-CoA:amino acid N-acyltransferase is an enzyme that catalyzes the chemical reaction
Cysteine sulfinic acid, also known as 3-sulfino-L-alanine, is an amino acid containing a sulfinic acid functional group. It is a white solid that is soluble in water. It is an intermediate in cysteine metabolism. It is not a coded amino acid, but is produced post-translationally.
Cysteic acid also known as 3-sulfo-l-alanine is the organic compound with the formula HO3SCH2CH(NH2)CO2H. It is often referred to as cysteate, which near neutral pH takes the form −O3SCH2CH(NH3+)CO2−.
Phenylsulfinic acid is an organosulfur compound with the formula C6H5SO2H. It is a colorless or white crystalline solid that is usually stored in the form of its sodium salt. In aqueous solution it is strongly acidic and is easily oxidized in air. Phenylsulfinic acid and its esters are chiral.
Thiourea dioxide or thiox is an organosulfur compound that is used in the textile industry. It functions as a reducing agent. It is a white solid. The compound exhibits tautomerism.
In biochemistry, non-coded or non-proteinogenic amino acids are those not naturally encoded or found in the genetic code of any organism. Despite the use of only 22 amino acids by the translational machinery to assemble proteins, over 140 amino acids are known to occur naturally in proteins and thousands more may occur in nature or be synthesized in the laboratory. Many non-proteinogenic amino acids are noteworthy because they are;
