Metabolism of a-Ketoaldehydes in Yeasts: Purification and Characterization of Glyoxalase II from Saccharomyces cerevisiae

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Glyoxalase II, that catalyzes the conversion of S-lactoylglutathione into lactate and glutathione, was isolated from the yeast, Saccharomyces cerevisiae, and some properties of the enzyme were determined. The glyoxalase II was purified approximately 100 fold from a cell extract with a 20% activity yield. Estimation of the molecular weight of the enzyme by both gel filtration and SDS/polyacrylamide gel electrophoresis gave a value of 1.9×104. Among the various thiol esters tested, the enzyme hydrolyzed only S-lactoylglutathione with a Km=70×10-6M. The enzyme was most active at low pH (pH 3-4) and was stable even in 0.001 N HCl at 40°C for at least 15 min. The activity of the enzyme was inhibited by various thiol compounds such as glutathione and coenzyme A. Hemimercaptal, a non-enzymatic condensation product of methylglyoxal and glutathione, strongly inhibited the activity of the enzyme.
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