FIGURE 4.

Glx3 is a glutathione-independent methylglyoxalase. The kinetics of wild-type Glx3 (filled circles) and the C136S mutant (open circles) are shown in hyperbolic representation, and the best fit Michaelis-Menten model is indicated with a solid line. Each rate was measured in triplicate, and mean values are plotted with standard deviations shown as error bars. At each concentration, the background uncatalyzed rate of MG degradation was measured and subtracted from the rate measured with enzyme present. The inactive C136S mutant demonstrates that the proposed catalytic nucleophile Cys¹³⁶ is essential for catalysis.