Methionine metabolism of the myxomycete Physarum polycephalum.

Daniel, John W. (University of Wisconsin, Madison), and Karlee Babcock. Methionine metabolism of the myxomycete Physarum polycephalum. J. Bacteriol. 92:1028-1035. 1966.-Previous studies have shown that Physarum polycephalum requires exogenous methionine for growth, but not cysteine, folic acid, or vitamin B(12). Methionine can also serve as the sole source of sulfur for all cellular requirements, without limiting the growth rate. S-methyl-l-cysteine, 2-hydroxy-4-methiol butyric acid, S-adenosyl-l-methionine, and methionine peptides were the only compounds supporting growth, when substituted for methionine. Other methionine analogues, methyl donors in combination with homocysteine, and intermediates of the cystathionine pathway were not active. Ethionine and S-ethyl cysteine were good methionine antagonists. This myxomycete is apparently unable to synthesize the methyl or S-methyl group, although it still appears able to transmethylate, at least from S-methyl cysteine, and probably from S-adenosyl methionine, which can also serve as a source of adenine.