Cysteinesulfinic acid decarboxylase

Werle and Pechmann 184) have presented evidence that diamine oxidase from plants could be activated by pyridoxal. The rate of inhibition of enzyme systems by isonicotinic acid hydrazide has been used as a means of detecting the presence of pyridoxal phosphate as a coenzyme, particularly when it is tightly bound to the apoenzyme 205, 206). Davison 166) has shown that the rates of inhibition of an established pyridoxal phosphate containing enzyme, cysteinesulfinic acid decarboxylase 207, 208), and diamine oxidase are similar and that pyridoxal phosphate will reactivate diamine oxidase after inhibition with isonicotinic acid hydrazide. On this basis it has been suggested that pyridoxal phosphate is probably involved as a coenzyme for diamine oxidase. 

The finding of a dietary requirement for taurine in the human infant is consistent with the negligible activity of cysteinesulfinic acid decarboxylase present both in fetal and in mature human liver (Gaull et al., 1977). 

To our knowledge the possibility that glutamate decarboxylase could operate also the decarboxylation of XI and XII has not been eliminated. Actually we have been surprised to find deleted out of the official Enzyme Nomenclature the name of cysteinesulfinic acid decarboxylase, formerly listed under the number 4.1.1.29, and now listed as a side property of glutamate decarboxylase registered under the number 4.1.1.15 (23). Decarbosylation of glutamate and that of XI and XII in rat brain have actually been reported to behave similarly under a set of various conditions (24), on the other hand the variation of the ratio of the decarboxylation rate of glutamate compared with that of XI of rat brain with age has been claimed as an indication of the occurrence of different enzymes (25). 

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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