No abstract

SummaryIn uence of H 2 O 2 on glycolysis was investigated. A hypothesis previously formulated was tested according to which a mild oxidation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) results in uncoupling of oxidation and phosphorylation at this step of glycolysis due to acylphosphatase activity of the oxidized enzyme. Incubation of a mixture of puri ed glycolytic enzymes, as well as a muscle extract, in the presence of 10 -100 ¹M H 2 O 2 was shown to result in an increase in the rate of glycolysis.

Mild oxidation of glyceraldehyde-3-phosphate dehydrogenase in the presence of hydrogen peroxide leads to oxidation of some of the active site cysteine residues to sulfenic acid derivatives, resulting in the induction of acylphosphatase activity. The reduced active sites of the enzyme retain the ability to oxidize glyceraldehyde-3-phosphate yielding 1,3-diphosphoglycerate, while the oxidized active sites catalyze irreversible cleavage of 1,3-diphosphoglycerate. It was assumed that the oxidation of glyceraldehyde-3-phosphate dehydrogenase by different physiological oxidants must accelerate glycolysis due to uncoupling of the reactions of oxidation and phosphorylation. It was shown that the addition of hydrogen peroxide to the mixture of glycolytic enzymes or to the muscle extract increased production of lactate, decreasing the yield of ATP. A similar effect was observed in the presence of non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase catalyzing irreversible oxidation of glyceraldehyde-3-phosphate into 3-phosphoglycerate. A role of glyceraldehyde-3-phosphate dehydrogenase in regulation of glycolysis is discussed.