title: Mitochondrial hydrogen peroxide formation and the fumarate reductase of Hymenolepis diminuta.
abstract: The catalysis of hydrogen peroxide accumulation by the mitochondrial, membrane-associated NADH oxidase and less active succinoxidase of adult Hymenolepis diminuta was confirmed. NADH-dependent peroxide formation by isolated mitochondrial membranes occurred at about half the coincident rates of NADH and oxygen utilization, whereas succinate-dependent peroxide formation accounted for approximately 40% of the oxygen consumed. These findings, coupled with evaluations of the oxidases, indicated that both systems use in common 2 mechanisms for oxygen reduction, 1 of which is peroxide-forming. Neither system was sensitive to cyanide, azide, or antimycin A. Rotenone inhibition of NADH oxidation resulted in equivalent decreases in oxygen consumption by the peroxide-forming and nonperoxide-forming mechanisms. In contrast, malonate inhibition occurred via disruption of the peroxide-forming mechanism. Fumarate stimulated membrane-catalyzed NADH oxidation, despite aerobic conditions, and this fumarate reductase was rotenone-sensitive. NADH- or succinate-dependent peroxide formation virtually was abolished and oxygen consumption was minimal in the presence of fumarate. Malonate also inhibited fumarate-dependent NADH oxidation and succinate-dependent peroxide formation/oxygen consumption. Collectively, these findings clearly indicate that NADH- or succinate-dependent hydrogen peroxide accumulation involves the malonate-sensitive fumarate reductase, in the absence of fumarate. A model of the H. diminuta electron transport system is presented.
authors.affiliation: Department of Biological Sciences, Bowling Green State University, Ohio 43403.
authors.forename: C F
authors.initials: CF
authors.lastname: Fioravanti
authors.forename: J M
authors.initials: JM
authors.lastname: Reisig
mesh_terms: D000818:Animals; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006926:Hymenolepis / Q000201:enzymology / Q000378:metabolism*; D008298:Maleates / Q000494:pharmacology; D008314:Malonates / Q000494:pharmacology; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D010101:Oxygen Consumption; D012402:Rotenone / Q000494:pharmacology; D013385:Succinate Dehydrogenase / Q000378:metabolism*; D013386:Succinates / Q000378:metabolism
chemical_list: D008298:Maleates; D008314:Malonates; D009097:Multienzyme Complexes; D013386:Succinates; D012402:Rotenone; D009243:NAD; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; C022691:succinate oxidase; D013385:Succinate Dehydrogenase; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases