This Pyruvaldehyde degradation pathway (Methylglyoxal degradation;2-oxopropanal degradation), also known as the glyoxalase system, is probably the most common pathway for the degradation of pyruvaldehyde (methylglyoxal), a potentially toxic metabolite due to its interaction with nucleic acids and other proteins. Pyruvaldehyde is formed in low concentrations by glycolysis, fatty acid metabolism and protein metabolism. Pyruvaldehyde is catalyzed by the glyoxylase system, composed of the enzymes lactoylglutathione lyase (glyoxalase I) and glyoxylase II. Glyoxalase I catalyes the isomerization of the spontaneously formed hemithioacetal adduct between glutathione and pyruvaldehyde into S-lactoylglutathione. S-lactoylglutathione is then catalyzed by glyoxalase II into D-lactic acid and glutathione. D-lactic acid is then catalyzed by an unknown quinol in the membrane to pyruvic acid, which then enters pyruvate metabolism.