METABOLIC REGULATION OF ADENOSINE TRIPHOSPHATE SULFURYLASE IN YEAST.

de Vito, Peter C. (Princeton University, Princeton, N.J.), and Jacques Dreyfuss. Metabolic regulation of adenosine triphosphate sulfurylase in yeast. J. Bacteriol. 88:1341-1348. 1964.-The metabolic regulation of adenosine triphosphate sulfurylase (ATP-sulfurylase) from baker's yeast was studied. The enzyme was strongly inhibited by low concentrations of adenosine-5'-phosphosulfate, 3'-phosphoadenosine-5'-phosphosulfate, and sulfide. Sulfide ion was a competitive inhibitor of ATP-sulfurylase. Cysteine, methionine, sulfite, and thiosulfate were not inhibitors of the enzyme. ATP-sulfurylase was repressed when yeast was grown in the presence of methionine, and derepressed when yeast was grown in the presence of cysteine. In contrast to these results, the enzyme sulfite reductase was repressed in cysteine-grown cells. Thus, the sulfate-reducing pathway in yeast appears to be regulated at its first step both by feedback inhibition (by sulfide) and by repression (by methionine). Other known controls in the cysteine biosynthetic pathway are discussed.