Anaerobic metabolism in Ascaris suum: acyl CoA intermediates in isolated mitochondria synthesizing 2-methyl branched-chain fatty acids.

Freshly isolated Ascaris suum mitochondria contained CoASH, acetyl CoA, propionyl CoA, 2-methylcrotonyl CoA, 2-methylbutyryl CoA, 2-methyl-2-pentenoyl CoA, and 2-methylvaleryl CoA, as determined by high-pressure liquid chromatography. Incubation of these mitochondria aerobically in the absence of substrate resulted in the conversion of the branched-chain enoyl CoA's to acetyl CoA and propionyl CoA. With the addition of malate to the incubation medium, succinyl CoA and methylmalonyl CoA accumulated and the levels of propionyl CoA decreased dramatically. However, the branched-chain fatty acids characteristic of A. suum's fermentative metabolism were not formed and it appears that the formation of propionyl CoA may be limiting in these mitochondria. Indeed, the addition of propionate to incubations with malate increased intramitochondrial levels of propionyl CoA and 2-methyl-2-pentenoyl CoA and stimulated significant 2-methylvalerate synthesis. The exclusion of air from these incubations further increased levels of 2-methyl-2-pentenoyl CoA and stimulated 2-methylvalerate synthesis. These studies suggest that in addition to elevated NADH/NAD ratios, elevated enoyl CoA/acyl CoA ratios also are important in the regulation of branched-chain fatty acid synthesis in A. suum mitochondria.