The GLO1 Gene Is Required for Full Activity of O-Acetyl Homoserine Sulfhydrylase Encoded by MET17

During glycolysis, yeast generates methylglyoxal (MG), a toxic metabolite that affects growth. Detoxification can occur when glyoxylase I (GLO1) and glyoxylase II (GLO2) convert MG to lactic acid. We have identified an additional, previously unrecognized role for GLO1 in sulfur assimilation in the yeast Saccharomyces cerevisiae. During a screening for putative carbon–sulfur lyases, the glo1 deletion strain showed significant production of H2S during fermentation. The glo1 strain also assimilated sulfate inefficiently but grew normally on cysteine. These phenotypes are consistent with reduced activity of the O-acetyl homoserine sulfhydrylase, Met17p. Overexpression of Glo1p gave a dominant negative phenotype that mimicked the glo1 and met17 deletion strain phenotypes. Western analysis revealed reduced expression of Met17p in the glo1 deletion, but there was no indication of an altered conformation of Met17p or any direct interaction between the two proteins. Unravelling a novel function in sulfur assimilat...