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Cysteine sulfinic acid is the 
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
with the nominal formula HO2SCH2CH(NH2)CO2H . It is a rare example of an amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
bearing a sulfinic acid functional group
In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest ...
. It is a white solid that is soluble in water. Like most natural amino acids, it is chiral, only the d-enantiomer occurs in nature, and it exists as the zwitterion at neutral pH. It is an intermediate in cysteine metabolism
Cysteine metabolism refers to the biological pathways that consume or create cysteine. The pathways of different amino acids and other metabolites interweave and overlap to creating complex systems.cysteine is metabolism creating complex systems
...
. It is not a coded amino acid, but is produced post-translationally. Peptides containing the cysteine sulfinic acid residue are substrates for cysteine sulfinic acid reductase.
Cysteine sulfinic acid is derived from cysteine
Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile.
When present as a deprotonated catalytic residue, sometime ...
. Cysteine is formed from cystathionine via the cystathionine gamma-lyase enzyme, and is either broken down by cysteine lyase or cystathionine gamma-lyase or enters the cysteine sulfinic acid pathway where it is oxidized by cysteine dioxygenase to form cysteine sulfinic acid. Cysteine sulfinic acid, in turn, is decarboxylated by sulfinoalanine decarboxylase
The enzyme sulfinoalanine decarboxylase () catalyzes the chemical reaction
:3-sulfino-L-alanine \rightleftharpoons hypotaurine + CO2
Hence, this enzyme has one substrate, 3-sulfino-L-alanine (also known as Cysteine sulfinic acid), and two produ ...
to form hypotaurine, which in turn is oxidized by hypotaurine dehydrogenase
In enzymology, a hypotaurine dehydrogenase () is an enzyme that catalysis, catalyzes the chemical reaction
:hypotaurine + H2O + NAD+ \rightleftharpoons taurine + NADH + H+
The 3 substrate (biochemistry), substrates of this enzyme are hypotaurine, ...
to yield taurine. Proteins containing this residue are found at the active site of some nitrile hydratase
Nitrile hydratases (NHases; ) are mononuclear iron or non-corrinoid cobalt enzymes that catalyse the hydration of diverse nitriles to their corresponding amides
R-C≡N + H2O → R-C(O)NH2
Metal cofactor
In biochemistry, cobalt is in general ...
s.Isao Endo, Masaki Nojiri, b, Masanari Tsujimura, Masayoshi Nakasako, Shigehiro Nagashima, Masafumi Yohda, Masafumi Odaka "Focused Review: Fe-type nitrile hydratase"Journal of Inorganic Biochemistry 2001, Volume 83, Issue 4, February 2001, Pages 247–253.
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