title: Coupling of "malic" enzyme and NADPH:NAD transhydrogenase in the energetics of Hymenolepis diminuta (Cestoda).
abstract: Acetylpyridine NADP replaced NADP in promoting the Mn2+ ion-requiring mitochondrial "malic" enzyme of Hymenolepis diminuta. Disrupted mitochondria displayed low levels of an apparent oxaloacetate-forming malate dehydrogenase activity when NAD or acetylpyridine NAD served as the coenzyme. Significant malate-dependent reduction of acetylpyridine NAD by H. diminuta mitochondria required Mn2+ ion and NADP, thereby indicating the tandem operation of "malic" enzyme and NADPH:NAD transhydrogenase. Incubation of mitochondrial preparations with oxaloacetate resulted in a non-enzymatic decarboxylation reaction. Coupling of malate oxidation with electron transport via the "malic" enzyme and transhydrogenase was demonstrated by polarographic assessment of mitochondrial reduced pyridine nucleotide oxidase activity.
mesh_terms: D000818:Animals; D003067:Coenzymes / Q000378:metabolism; D004579:Electron Transport; D004734:Energy Metabolism; D006926:Hymenolepis / Q000201:enzymology*; D008291:Malate Dehydrogenase / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000201:enzymology*; D009243:NAD / Q000031:analogs & derivatives / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D009250:NADP Transhydrogenases / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains / Q000469:parasitology
chemical_list: D003067:Coenzymes; D009243:NAD; C005941:3-acetylpyridine adenine dinucleotide; D008291:Malate Dehydrogenase; D009247:NADH, NADPH Oxidoreductases; D009250:NADP Transhydrogenases