β-Oxidation of the coenzyme a esters of elaidic, oleic, and stearic acids and their full-cycle intermediates by rat heart mitochondria

Abstract

β-Oxidation rates for the CoA esters of elaidic, oleic and stearic acids and their full-cycle β-oxidation intermediates and for the carnitine esters of oleic and elaidic acids were compared over a wide range of substrate and albumin concentrations in rat heart mitochondria. The esters of elaidic acid were oxidized at about half the rate of the oleic acid esters, while stearoyl-CoA was oxidized equally as rapid as oleoyl-CoA. The full-cycle β-oxidation intermediates of elaidoyl-CoA ( trans-16 : 1 Δ 7, −14 : 1 Δ 5, and −12 : 1 Δ 3) were found to be oxidized at rates nearly equal to those for the corresponding intermediates of oleoyl-CoA. Therefore, after the first cycle of β-oxidation, oleoyl-CoA and elaidoyl-CoA are oxidized at nearly equal rates. The activity of fatty acyl-CoA dehydrogenase was higher with elaidoyl-CoA and its full-cycle intermediates as substrates than with the corresponding cis isomers. It was concluded that the slower oxidation rate of elaidic acid is not due to slower oxidation of any of its full-cycle β-oxidation intermediates, nor to slower activity of fatty acyl-CoA dehydrogenase, nor to outer mitochondrial carnitine acyltransferase. Possible explanations to account for the slower oxidation rate of elaidic acid are discussed.