Cysteinesulfonic acid

HT is oxidized to TA, probably with the help of HT oxidase70. Recently Fellman presented evidence that HT is first oxidized by a hydroxyl radical to bis-aminoethyl-a-disulfone 26. The hydroxyl radical is generated by a liver microsomal NADPH oxidase. 26 has been prepared from HT in the presence of chemically or enzymatically generated radicals and was characterized by NMR and mass spectrometry. It has been found in male sexual tissue which contains HT and TA in respectively high concentrations83. A relatively minor pathway consists of oxidation of CSA to cysteic acid (cysteinesulfonic acid, CA 27) and its decarboxylation to TA under the influence of CSA decarboxylase70. 

Cysteinesulfinic Acid. Cysteine is oxidized by enzyme systems present in bacteria and in liver to the corresponding sulfinic acid. It has been suggested that the unstable sulfenic acid is an intermediate in this oxidation. The nature of the reaction that produces cysteinesulfinic acid is not known. The subsequent metabolism of the sulfinic acid may proceed by any of three pathways. One involves further oxidation to cysteine-sulfonic acid, cysteic acid. The enzyme responsible has not been separated from the system responsible for the formation of cysteinesulfinic acid. Cysteinesulfonic acid is decarboxylated to taurine (I) by the decarboxylase mentioned previously (p. 284). 

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