ChEBI: Cysteic acid is an amino sulfonic acid that is the sulfonic acid analogue of cysteine. It has a role as an animal metabolite. It is an alanine derivative, an amino sulfonic acid, a carboxyalkanesulfonic acid, a cysteine derivative and a non-proteinogenic alpha-amino acid.
Likely impurities are cystine and oxides of cysteine. Crystallise the acid from water by adding 2 volumes of EtOH. It crystallises from H2O as the monohydrate. When recrystallised from aqueous MeOH it has m 264-266o, and the anhydrous acid has m ~260o(dec). [Chapeville & Formageot Biochim Biophys Acta 26 538 1957, Gortner & Hoffman J Biol Chem 72 435 1927, Greenstein & Winitz The Chemistry of the Amino Acids J. Wiley, Vol 3 p1908 1961.]
