Cysteine sulfinic acid
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.
Cysteine sulfinic acid is derived from cysteine. 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 to form hypotaurine, which in turn is oxidized by hypotaurine dehydrogenase to yield taurine. Proteins containing this residue are found at the active site of some nitrile hydratases.
