Cysteic acid also known as 3-sulfo--alanine 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 formula HO₃SCH₂CH(NH₂)CO₂H. It is often referred to as cysteate, which near neutral pH takes the form ⁻O₃SCH₂CH(NH₃⁺)CO₂⁻. It is 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 ...

generated by oxidation of

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 ...

, whereby a thiol group is fully oxidized to a

sulfonic acid In organic chemistry, sulfonic acid (or sulphonic acid) refers to a member of the class of organosulfur compounds with the general formula , where R is an organic alkyl or aryl group and the group a sulfonyl hydroxide. As a substituent, it is kn ...

/sulfonate group. It is further metabolized via 3-sulfolactate, which converts to pyruvate and sulfite/bisulfite. The enzyme

L-cysteate sulfo-lyase The enzyme L-cysteate sulfo-lyase (EC 4.4.1.25) catalyzes the reaction :L-cysteate + H2O = hydrogensulfite + pyruvate + NH3 (overall reaction) ::(1a) L-cysteate = hydrogensulfite + 2-aminoprop-2-enoate ::(1b) 2-aminoprop-2-enoate = 2-iminopropa ...

catalyzes this conversion. Cysteate is a biosynthetic precursor to

taurine 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. It ...

in microalgae. By contrast, most taurine in animals is made from cysteine sulfinate.

References

Sulfur amino acids Sulfonic acids {{organic-compound-stub