Purification and kinetic study of glyoxalase-I from rat liver, erythrocytes, brain and kidney.

Glyoxalase-I (S-lactoyl-glutathione methylglyoxal-lyase (isomerizing), EC 4.4.1.5) was purified from rat liver, erythrocytes, brain and kidney using two different purification procedures. The similarities of the purification profiles, electrophoretic mobilities and kinetics suggest that a single major form of the enzyme exists in these tissues. The highest purification (9300-fold) of the erythrocyte enzyme gave nearly homogeneous protein, molecular weight 50 000, specific activity 2410 mumol/min per mg. Kinetic studies of the rat glyoxalase-I-catalyzed disproportionation of the hemimercaptals of GSH and aromatic or aliphatic alpha-ketoaldehydes revealed broad substrate specificity with V and Km values quite insensitive to the nature of the alpha-ketoaldehydes. Use of deuterated analogs of the alpha-ketoaldhydes methylglyoxal and phenylglyoxal showed that the intramolecular hydride migration is the rate-determining step.