Formation of Methylglyoxal From Hexose Phosphate by Tissues.

Abstract

Methyl glyoxal has long been hypothecated as a probable intermediate in the formation of lactic acid in tissues, for which hypothesis the existence of glyoxalase activity is strong but indirect evidence. Until very recently methyl glyoxal has never been detected in tissues. Toenniessen and Fisher now report that hexose phosphate with muscle in the presence of pancreas (anti-glyoxalase) forms methyl glyoxal which they were able to identify by the p-nitro-phenyl-di-hydrazone. In attempting to repeat this work I find that if muscle, or, better yet, liver extract when incubated with toluol for 24 hours, then hexose phosphate added and the mixture incubated for another day, the solution contains a substance which reacts like methyl glyoxal. It may be determined by the colorimetric method, is destroyed by excess alkali as is methyl glyoxal, and it gives a red di-hydrozone with p-nitro-phenyl-hydrazine which after recrystallization from pyridin melts with decomposition at about 283° (uncorrected). The di-hydrazone made from methyl glyoxal has the same crystal form and melting point. This evidence confirms the observation of Toeniessen and Fisher and indicates that the substance is actually methyl glyoxal; but conclusion is withheld until a larger quantity of the substance is prepared and submitted for further analysis. The importance of this observation makes very desirable a detailed investigation of the reactions involved. Hexose phosphate alone, liver (or muscle) extract alone, or heated extract plus hexose phosphate does not yield the glyoxal-like substance. The formation of methylglycixal under the conditions stated perhaps indicates that the conversion of hexose phosphate to lactic acid takes place in steps, hexose phosphate → methyl glyoxal → lactic acid. The glyoxalase, responsible for the second step is largely destroyed during the first day of autolysis, while the ferment presumably responsible for the first step (pliosphatase) is apparently still active.