Catalyzes the conversion of hemimercaptal, formed from methylglyoxal and glutathione, to S-lactoylglutathione. (R)-S-lactoylglutathione = glutathione + methylglyoxal Binds 1 zinc ion per subunit. Secondary metabolite metabolism; methylglyoxal degradation; (R)-lactate from methylglyoxal: step 1/2. On the 2D-gel the determined pI of this protein is: 5.7, its MW is: 35.1 kDa. Belongs to the glyoxalase I family. The order of the peptides shown is unknown.