Glyoxalase I [S-lactoylglutathione methylglyoxal-lyase (isomerizing) EC 4.4. 1.5; GX I] catalyzes the conversion of the thiohemiacetal 2 of a-keto aldehyde l and glutathione [N-(NL- ~-glutamyl-L-cysteiny1) glycine; GSH] to the thioester 4 of an a-hydroxy acid and GSH (Scheme I).] The reaction proceeds via a fast-shielded proton transfer with the intermediacy of enediol 3, 2 and the resulting acid has been established as the D i~ omer.~ Recent'H ...