Phospholipid Dependency of Membrane-Associated Pyridine Nucleotide-Utilizing and Succinate Dehydrogenase Activities of Adult Hymenolepis Diminuta (Cestoda) and Ascaris Suum (Nematoda)
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The adult intestinal cestode, Hymenolepis diminuta, is essentially anaerobic in its metabolism and generates ATP without the need for oxygen. H. diminuta relies upon a mitochondrial NADPH->NAD transhydrogenase to link the NADPH produced by the pyruvate-forming arm of the malate dismutation reaction, catalyzed by the mitochondrial “malic enzyme”, with the NADH-requiring, anaerobic electron transport system. The electron transport-coupled fumarate reductase serves to reduce fumarate, the terminal electron acceptor, to succinate. A phospholipid dependency was established previously with respect to the transhydrogenase, fumarate reductase, and the lesser NADH oxidase. Of the phospholipids assessed, the transhydrogenase exhibited a phosphatidylcholine preference.
The present study expands on prior findings by using phospholipase A1, A2, C and D, organic solvent, and ammonium sulfate treatments of H. diminuta mitochondrial membranes. Other reduced pyridine nucleotide-utilizing systems viz., NAD(P)H cytochrome c reductase, NADH->NAD transhydrogenation, NAD(P)H-, and lipoamide dehydrogenase activities as well as succinate dehydrogenase were evaluated. A comparative study also was undertaken by treatment with the phospholipases of isolated mitochondrial membranes from the anaerobic intestinal nematode, Ascaris suum.
The data presented indicate a phospholipid dependence not only of the previously reported systems, but of membrane-associated mitochondrial systems in H. diminuta and A. suum. H. diminuta NADH cytochrome c reductase displayed phospholipid dependence based on phospholipase A2 and C treatments, and a neutral lipid dependence based on organic solvent treatments. Ammonium sulfate fractionation had little effect. Succinate dehydrogenase activity displayed phospholipid dependence based on phospholipase C and organic solvent treatments. Ammonium sulfate fractionation decreased succinate dehydrogenase activity, but phosphatidylcholine supplementation further diminished activity.
A. suum NADH cytochrome c reductase, NADH oxidase and fumarate reductase systems exhibited phospholipid dependence based on phospholipase A2 and C treatments. Interestingly, A. suum succinate dehydrogenase appeared more resistant to phospholipase treatment than the corresponding H. diminuta system.
Document number: bgsu1343921911
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1343921911
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