Mitochondrial hydrogen peroxide production as determined by the pyridine nucleotide pool and its redox state

The rates of NADH-supported superoxide/hydrogen peroxide production by membrane-bound bovine heart respiratory complex I. soluble pig heart dihydrolipoamide dehydrogenase (DLDH), and by accompanying operation of these enzymes in rat heart mitochondrial matrix were measured as a function of the pool of pyridine nucleotides and its redox state. Each of the activities showed nontrivial dependence on nucleotide pool concentration. The NAD(+)/NADH ratios required for their half maximal capacities were determined. About half of the total NADH-supported H2O2 production by permeabilized mitochondria in the absence of stimulating ammonium could be accounted for by DLDH activity. The significance of the mitochondrial NADH-dependent hydrogen peroxide production under physiologically relevant conditions is discussed. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012). (C) 2012 Elsevier B.V. All rights reserved.