Oxidative phosphorylation in Moniezia muscle mitochondria

Abstract

1. 1. Mitochondria isolated from Moniezia expansa, an intestinal parasitic tapeworm, have the same structural characteristics as the classical mammalian aerobic mitochondria by having clearly defined outer and inner membranes, outer compartment and intracristal spaces, and elementary particles attached to the mitochondrial cristae. 2. 2. Intact Moniezia mitochondria are impermeable to NADH. The oxidation of α-glycerophosphate, succinate and ascorbate plus tetramethyl- p-phenylenediamine (TMPD), l-malate, pyruvate plus malate and l-glutamate plus malate, l-glutamate and pyruvate (in decreasing order of activity) was stimulated by ADP. Succinate oxidation has a K m of 28 μM ADP. 3. 3. α-Glycerophosphate and succinate oxidation have an ADP/O ratio of 1.5. Oxidative phosphorylation in Moniezia was inhibited by the classical mammalian inhibitors, oligomycin and atractyloside, and the oligomycin inhibition could be relieved by the uncoupler, p-trifluoromethoxycarbonylcyanidephenylhydrazone (FCCP). 4. 4. The oxidation of the NAD +-linked substrate, pyruvate plus malate, was piericidin A sensitive. Complete inhibition of the State 3 rate was achieved at 50 pmoles piericidin A per mg mitochondrial protein. 5. 5. 8.0 ng antimycin A (approx. 16 pmoles) per mg mitochondrial protein inhibited 50% of the succinoxidase activity (State 3). 33% of Moniezia mitochondrial respiration (State 3) with succinate as substrate was antimycin A insensitive from about 20 to 230 ng antimycin A per mg protein. 6. 6. α-Glycerophosphate, succinate and cytochrome oxidase (EC1.9.3.1) activities were very sensitive to CN −. The amount of CN − required to give 50% inhibition ( K i ) was 8μM (without FCCP) and 24 μM (with FCCP) for succinate oxidation (State 3), and 20 μM (with FCCP) for both the α-glycerophosphate and cytochrome oxidase activities (State 3).