Methylglyoxal Binding to Bovine Liver Catalase Results in Loss of Activity and Heme Dislocation

Glycation, the non-enzymatic attachment of glucose to protein, is one of the important events in the pathophysiology of diabetes mellitus, Alzheimer’s, Parkinson’s and other diseases. Methylglyoxal (MG), a dicarbonyl compound formed during glycation, monosaccharide autoxidation, and metabolism is elevated during diabetes mellitus. Among other antioxidant enzymes, catalase is important for the defense against oxidative damage. However, antioxidant enzymes including catalase can themselves become targets of non-enzymatic modification by methylglyoxal. In this study, catalase was incubated with increasing concentrations of MG for different time intervals. Structural and functional alterations to catalase were monitored by a variety of approaches, namely, assay of enzyme activity, staining of gels for activity as well as heme, measurement of protein carbonyls and Arg pyrimidine, which is a specific MG modification product. A progressive increase in electrophoretic mobility and detachment of heme from the monomer were observed with increasing concentrations of methylglyoxal. The MG-modified enzyme showed reduced affinity towards the substrate hydrogen peroxide. Molecular modeling studies revealed that MG can access the heme and arginine residues close to it. Thus, the decrease in activity of methylglyoxal-modified catalase may be important in aggravating the severity of secondary complications seen in diabetes mellitus.HIGHLIGHTS•Increase in concentration of methylglyoxal caused a progressive increase in electrophoretic mobility and detachment of heme from the monomer.•MG-modified enzyme showed reduced affinity towards the substrate hydrogen peroxide.•Molecular modeling studies showed that MG can access the heme and arginine residues close to it.