Biosynthesis of S-adenosylmethionine by Saccharomyces cerevisiae. I. Adenine and methionine requirments

Abstract

Yall, Irving (University of Arizona, Tucson, Ariz.). Biosynthesis of S-adenosylmethionine by Saccharomyces cerevisiae. I. Adenine and methionine requirements. J. Bacteriol. 83:1336-1340. 1962.-Both a parent strain (SC-10) and an adenineless mutant strain (SC-10-80-3-5) of Saccharomyces cerevisiae accumulated S-adenosylmethionine (AM) in the presence of "excess" l-methionine (400 mumoles/100 ml of medium). Relatively small amounts of AM were found when the organisms were grown in the absence of methionine, in the presence of "normal" amounts of l-methionine (3.35 mumoles/100 ml of medium), or in the presence of 400 mumoles of d-methionine. Adenine and hypoxanthine were equally effective in promoting cell growth and AM production in the mutant. S-adenosylmethionine permitted some cell growth. Other purines (guanine and xanthine) and nucleosides such as adenosine and methylthioadenosine did not serve as growth factors. The cell permeability to adenosine was tested by growing the parent strain in the presence of adenosine-8-C(14) and the mutant in adenine and the labeled nucleoside. Both of these experiments were performed in the absence and presence of "excess" l-methionine. Under all conditions, more than 25% of the radioactivity introduced as adenosine-8-C(14) was found in the cells. About 40% of the radioactivity taken up by the mutant cells in the prescene of "excess" l-methionine was fixed in AM. Adenine-8-C(14) was readily taken up by cells of both strains when grown in the absence and presence of "excess" l-methionine. About 17% of the radioactivity taken up by the mutant cells in the presence of "excess" l-methionine was found in the AM fraction.