The Glyoxalase System in Rat Blood

Publisher Website
Google Scholar
Abstract
The 3-carbon keto-aldehyde, methylglyoxal (MeG), inhibits growth in bacterial and mammalian systems. The glyoxalase enzyme system catalyzes the catabolism of the .alpha.,.beta.-dicarbonyl to form D-lactate with glutathione (GSH) as a cofactor. Glyoxalase I (S-lactoyl-glutathione methylglyoxal-lyase, isomerizing; EC 4.4.1.5) and glyoxalase II (S-2-hydroxyacylglutathione hydrolase; EC 3.1.2.6) are present in mammalian tissues and have a high specific activity in red blood cells. To determine possible changes in the glyoxalase system with growth, the various components of the glyoxalase system were measured in the blood of male Sprague-Dawley rats aged 20-89 days. Glyoxalase I and II kinetic parameters were determined in potassium phosphate buffer at pH 6.8. Glutathione reductase activity, blood concentration of GSH and protein, plasma concentration of D-lactate and hematocrit were also measured. The mean V [velocity] for glyoxalase I was 81 .mu.mol/min per ml of red blood cells as compared to the glyoxalase II catalysis of S-lactoyl-glutathione (SLG) to D-lactate of 48 .mu.mol/min per ml. The mean Km values for MeG and SLG were 0.9 and 1.2 mM, respectively. The Km and V for the glyoxalase enzymes were not age dependent in the growing animal when controlled for changes in hematocrit and protein. Only D-lactate plasma concentration showed a positive correlation with age (P < 0.005) when hematocrit and protein changes were controlled. The increase in D-lactate may indicate an increased formation of MeG with potential for cellular inhibition.