Taurine glutamate decarboxylase

Pharmacological evidence was obtained several years ago that indicated that tryptophan is decarboxylated to tryptamine by both animal and bacterial enzymes. More recent studies have failed to detect this reaction, but instead have shown decarboxylation to occur only after oxidation of the indole nucleus to yield 5-hydroxytryptophan. Decarboxylation of 5-hydroxytryptophan produces 5-hydroxytryptamine, serotonin, which has important, though incompletely defined functions in animal physiology. In some animal livers there is an enzyme that decarboxylates cysteic acid to taurine. Glutamic decarboxylase has been found in animal brain, where it is responsible for the formation of 7-aminobutyric acid. This product has been implicated in nervous function as an inhibitor of synaptic transmission. ... 

Figure 14.7. Pathways for the synthesis of taurine from cysteine. Cysteine sulfinate decarboxylase, EC 4.1.1.29 cysteic acid decarboxylase, EC 4.1.1.29 (glutamate decarboxylase, EC 4.1.1.15) cysteine oxidase, EC 1.13.11.20 cysteamine oxygenase, EC 1.13.11.19 and hypotaurine oxidase, EC 1.8.1.3. Relative molecular masses (Mr) cysteine, 121.2 cysteamine, 77.2 cysteine sulfinic acid, 153.2 cysteic acid, 169.2 hypotaurine, 109.1 and taurine, 125.1.

Some pyridoxal phosphate-dependent enzymes are normally fuUy saturated with cofactor and show the same activity on assay in vitro whether additional pyridoxal phosphate is present in the incubation medium or not. Examples of this class of enzymes include liver cysteine sulfinate decarboxylase (which is involved in the synthesis of taurine from cysteine Section 14.5.1) and the brain and liver glutamate and aspartate aminotransferases. 

Rassin D K., Sturman J A, and Gaull G E, (1981) Sulfur ammo acid metabolism m the developing rhesus monkey brain. Subcellular studies of taurine, cysteinesulfmic acid decarboxylase, 7-amino-butyric acid, and glutamic add decarboxylase, / Neurochem 37, 740-748... 

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