The Synthesis of Taurine from Sulfate V. Regulatory Modifiers of the Chick Liver Enzyme System

Abstract

The activity of the enzyme system which produces taurine from PAPS and serine in chick liver has been tested for regulation by intermediates of the transsulfuration pathway. The l-isomer of methionine, SAM, homocysteine, cysteine, and CSA produced significant decreases in the activity of this enzyme system. Low concentrations of d-methionine, and isethionate, a product of taurine deamination, gave a slight enhancement of enzyme activity. Cysteic acid, a postulated enzyme-bound intermediate of this enzyme system, produced increased activity at low enzyme-protein concentration but no effect at higher concentrations. These data suggest the existence of a switchover mechanism in the biosynthesis of taurine in the animal from these two sulfur sources.