The formation of methylglyoxal from triose phosphates

<jats:p>In Krebs‐Ringer phosphate buffer, the rate of formation of methylglyoxal from glycerone phosphate and glyceraldehyde 3‐phosphate was first order with respect to the triose phosphate with rates constant values of 1.94 ± 0.02 × 10<jats:sup>−5</jats:sup> s<jats:sup>−1</jats:sup> (<jats:italic>n</jats:italic>= 18) and 1.54 ± 0.02 × 10<jats:sup>−4</jats:sup> s<jats:sup>−1</jats:sup> (<jats:italic>n</jats:italic>= 18) at 37°C, respectively. The rate of formation of methylglyoxal from glycerone phosphate and glyceraldehyde 3‐phosphate in the presence of red blood cell lysate was not significantly different from the nonenzymatic value (<jats:italic>P</jats:italic> > 0.05). Methylglyoxal formation from glycerone phosphate was increased in the presence of triose phosphate isomerase but this may be due to the faster non‐enzymatic formation from the glyceraldehyde 3‐phosphate isomerisation product. For red blood cells <jats:italic>in vitro</jats:italic>, the predicted non‐enzymatic rate of formation of methylglyoxal from glycerone phosphate and glyceraldehyde 3‐phosphate may account for the metabolic flux through the glyoxalase system. The reactivity of glycerone phosphate and glyceraldehyde 3‐phosphate towards the non‐enzymatic formation of methylglyoxal under physiological conditions suggests that methylglyoxal formation is unavoidable from the Embden‐Meyerhof pathway.</jats:p>