Purification and characterization of two forms of glyoxalase II from the liver and brain of Wistar rats.

Glyoxalase II (S-(2-hydroxyacyl)glutathione hydrolase, EC 3.1.2.6) was purified to homogeneity and separated into two forms (alpha, pI = 8.0; beta, pI = 7.4) from both liver and brain of wistar rats by column isoelectric focusing. These forms were also found to have different electrophoretic mobilities. No significant differences were found between the alpha and beta forms from either source in the relative molecular mass (about 24,000) or in Km values using three substrates. The temperature-inactivation profiles were also similar, the two forms being stable up to 50 degrees C. Chemical modification studies with phenylglyoxal suggest that these enzyme forms probably contain arginine residues near the active site. Inactivation of alpha and beta forms by diethylpyrocarbonate and by photooxidation with methylene blue, and protection by S-D-mandeloylglutathione, a slowly reacting substrate, suggest the presence of histidine at the active site. The alpha and beta forms show different half-life values in inactivation by histidine reagents, which may be due to a difference in the active-site structures of these enzymes. The results probably indicate distinct structures (sequences) for alpha and beta forms.