Peroxisomal beta-oxidation is a significant pathway for catabolism of fatty acids in a marine teleost

Hepatic beta-oxidation is characterized in a marine teleost, Myoxocephalus octodecimspinosus, to determine mitochondrial and peroxisomal substrate selectivity as well as metabolic partitioning. Substrate selectivity is broad for peroxisomal beta-oxidation. Acyl CoA oxidase activities, with all unsaturated substrates measured, are at least 35% of activity with palmitoyl CoA (16:0), a saturated substrate. Mitochondrial selectivities are more pronounced. Carnitine palmitoyltransferase activity with a monounsaturate, palmitoleoyl CoA (16:1), is nearly 40% greater than activity with palmitoyl CoA, whereas activities with two polyunsaturates are < 10% of activity with the saturate. The presence of polyunsaturated acyl CoA esters inhibits up to 70% the oxidation of palmitoyl CoA by intact peroxisomes. Acyl CoA hydrolase activity is localized to peroxisomal fractions prepared by density-gradient centrifugation. Hydrolytic activity in these fractions is nearly twofold the activity of beta-oxidation. Estimates for metabolic partitioning suggest that at least 50% of hepatic beta-oxidation may be initiated by the peroxisomal compartment.