title: Production of superoxide/hydrogen peroxide by the mitochondrial 2-oxoadipate dehydrogenase complex.
abstract: In humans, mutations in dehydrogenase E1 and transketolase domain containing 1 (DHTKD1) are associated with neurological abnormalities and accumulation of 2-oxoadipate, 2-aminoadipate, and reactive oxygen species. The protein encoded by DHTKD1 has sequence and structural similarities to 2-oxoglutarate dehydrogenase, and the 2-oxoglutarate dehydrogenase complex can produce superoxide/H2O2 at high rates. The DHTKD1 enzyme is hypothesized to catalyze the oxidative decarboxylation of 2-oxoadipate, a shared intermediate of the degradative pathways for tryptophan, lysine and hydroxylysine. Here, we show that rat skeletal muscle mitochondria can produce superoxide/H2O2 at high rates when given 2-oxoadipate. We identify the putative mitochondrial 2-oxoadipate dehydrogenase complex as one of the sources and characterize the conditions that favor its superoxide/H2O2 production. Rates increased at higher NAD(P)H/NAD(P)(+) ratios and were higher at each NAD(P)H/NAD(P)(+) ratio when 2-oxoadipate was present, showing that superoxide/H2O2 was produced during the forward reaction from 2-oxoadipate, but not in the reverse reaction from NADH in the absence of 2-oxoadipate. The maximum capacity of the 2-oxoadipate dehydrogenase complex for production of superoxide/H2O2 is comparable to that of site IF of complex I, and seven, four and almost two-fold lower than the capacities of the 2-oxoglutarate, pyruvate and branched-chain 2-oxoacid dehydrogenase complexes, respectively. Regulation by ADP and ATP of H2O2 production driven by 2-oxoadipate was very different from that driven by 2-oxoglutarate, suggesting that site AF of the 2-oxoadipate dehydrogenase complex is a new source of superoxide/H2O2 associated with the NADH isopotential pool in mitochondria.
authors.affiliation: The Buck Institute for Research on Aging, Novato, CA 94945, USA. Electronic address: rgoncal@hsph.harvard.edu.
authors.forename: Renata L S
authors.initials: RL
authors.lastname: Goncalves
authors.affiliation: A.N. Belozersky Institute of Physico-Chemical Biology and Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119991, Russia.
authors.forename: Victoria I
authors.initials: VI
authors.lastname: Bunik
authors.affiliation: The Buck Institute for Research on Aging, Novato, CA 94945, USA.
authors.forename: Martin D
authors.initials: MD
authors.lastname: Brand
mesh_terms: D000272:Adipates / Q000378:metabolism*; D000818:Animals; D005260:Female; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007655:Ketoglutarate Dehydrogenase Complex / Q000502:physiology*; D007700:Kinetics; D008931:Mitochondria, Muscle / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000201:enzymology; D010084:Oxidation-Reduction; D017208:Rats, Wistar; D013481:Superoxides / Q000378:metabolism*
chemical_list: D000272:Adipates; D013481:Superoxides; C001918:alpha-ketoadipic acid; D006861:Hydrogen Peroxide; D007655:Ketoglutarate Dehydrogenase Complex
keywords: 2-Oxoacid dehydrogenase complexes; 2-Oxoadipic acid dehydrogenase; DHTKD1; ROS; Reactive oxygen species; Skeletal muscle mitochondria