Figure 1.

Under normal physiological conditions, methylglyoxal (MG) is formed in plants during glycolysis and photosynthesis from dihydroxyacetone phosphate, which is catalyzed by triose phosphate isomerase to form glyceraldehyde 3-phosphate (Richard, 1993). The intermediate enediolate-P is formed in this reaction, which, after losing a phosphoryl group by beta-elimination, forms enol, which in turn is converted into MG. The reactions between the intermediate enediol and MG are non-enzymatic (blue arrows). The MG formed is eliminated by the sequential actions of glyoxalase I and II, in which the consumption and regeneration of reduced glutathione occurs.