Metabolism of 2-ketoaldehydes in mold: purification and characterization of glyoxalase I from Aspergillus niger

Glyoxalase I catalyzing the conversion of methylglyoxal into S-lactoylglutathione in the presence of glutathione was purified approximately 1,400-fold with 2.9% activity yield from mold, Aspergillus niger. The enzyme consisted of a single polypeptide chain with a relative molecular weight of 36,000 on both SDS-polyacrylamide gel electrophoresis and Sephadex G-150 gel filtration. The enzyme was most active at pH 7.0, 35-37 degrees C. Among the various aldehydes tested, the enzyme was active on methylglyoxal and 4,5-dioxovalerate with Km values of 1.25 and 0.87 mM, respectively. The activity of the enzyme was completely inhibited by Zn2+ at 0.5 mM. An equimolar amount of EDTA (0.5 mM) protected the enzyme from inactivation by Zn2+. EDTA competitively (K1 = 1.3 mM) inhibited the activity of the enzyme. Fe2+ was a potent activator for the enzyme, the activation being approximately 2.4-fold at 0.5 mM.