Expression of the glyoxalase I gene of Saccharomyces cerevisiae is regulated by high osmolarity glycerol mitogen-activated protein kinase pathway in osmotic stress response

Methylglyoxal is a cytotoxic metabolite derived from dihydroxyacetone phosphate, an intermediate of glycolysis, Detoxification of methylglyoxal is performed by glyoxalase I, Expression of the structural gene of glyoxalase I (GLO1) of Saccharomyces cerevisiae under several stress conditions was investigated using the GLO1-lacZ fusion gene, and expression of the GLO1 gene was found to be specifically induced by osmotic stress, The Hog1p is one of the mitogen-activated protein kinases (MAPKs) in S. cerevisiae, and both Msn2p and Msn4p are the transcriptional regulators that are thought to be under the control of Hog1p-MAPK. Expression of the GLO1 gene under osmotic stress was completely repressed in hog1 Delta disruptant and was repressed approximately 80 and 50% in msn2 Delta and msn4 Delta disruptants, respectively, A double mutant of the MSN2 and MSN4 gene was unable to induce expression of the GLO1 gene under highly osmotic conditions, Glucose consumption increased approximately 30% during the adaptive period in osmotic stress in the wild type strain, On the contrary, it was reduced by 15% in the hog1 Delta mutant, When the yeast cell is exposed to highly osmotic conditions, glycerol is synthesized as a compatible solute, Glycerol is synthesized from glucose, and a rate-limiting enzyme in glycerol biosynthesis is glycerol-3-phosphate dehydrogenase (GPD1 gene product), which catalyzes reduction of dihydroxyacetone phosphate to glycerol 3-phosphate. Expression of the GPD1 gene is also under the control of Hog1p-MAPK. Methylglyoxal is also synthesized from dihydroxyacetone phosphate; therefore, induction of the GLO1 gene expression by osmotic stress was thought to scavenge methylglyoxal, which in creased during glycerol production for adaptation to osmotic stress.