The Synthesis of Taurine from Sulfate III. Further Evidence for the Enzymatic Pathway in Chick Liver 1

Abstract

Summary

The purpose of this research was to determine the enzymatic pathway for the synthesis of taurine from inorganic sulfate in chick liver. The enzymatically active proteins were obtained in the supernatant fraction from an ammonium sulfate precipitate (0.7 saturation) of chick liver homogenate using carboxymethylcellulose (CMC)-ion exchange chromatography. Experiments designed to ascertain the acceptor of the sulfate from 3′-phosphoadenosine-5′-phosphosulfate (PAPS) indicated that serine had the highest activity. Further, pyridoxal phosphate-dependent serine dehy-drase activity was required in the reaction utilizing serine to form taurine. The formation of taurine was preceded by the intermediate being converted to enzyme-bound cysteic acid. Inhibition studies indicated that PAPS-transferase, serine dehydrase, cysteic acid decarboxylase activities were required for this reaction, as well as a sulfhydryl requirement.