Substrate selectivities differ for hepatic mitochondrial and peroxisomal beta-oxidation in an Antarctic fish, Notothenia gibberifrons.
Hepatic mitochondrial and peroxisomal beta-oxidation were examined in an Antarctic marine teleost, Notothenia gibberifrons. Enzymic profiles and rates of beta-oxidation by intact organelles were determined by using a range of fatty acyl-CoA substrates to evaluate substrate preferences. Partitioning of beta-oxidation between organelles was estimated. Substrate selectivities are broader for peroxisomal beta-oxidation than for mitochondrial beta-oxidation. Mitochondria show marked preference for the oxidation of a monounsaturated substrate, palmitoleoyl-CoA (C16:1), and two polyunsaturates, eicosapentaenoyl-CoA (C20:5) and docosahexaenoyl-CoA (C22:6). Carnitine palmitoyltransferase activities with palmitoleoyl-CoA (C16:1) are 2.4-fold higher than activities with palmitoyl-CoA (C16:0). Most polyunsaturated acyl-CoA esters measured appear to inhibit by over 40% the oxidation of palmitoyl-CoA by peroxisomes. Our findings suggest that the polyunsaturates, eicosapentaenoic acid (C20:5) and docosahexaenoic acid (C22:6), found in high concentrations in Antarctic fishes [Lund and Sidell (1992) Mar. Biol. 112, 377-382], are utilized as fuels to support aerobic energy metabolism. Metabolic capacities of rate-limiting enzymes and beta-oxidation rates by intact organelles indicate that up to 30% of hepatic beta-oxidation in N. gibberifrons can be initiated by the peroxisomal pathway.
Crockett
E L
EL
Department of Zoology, University of Maine, Orono 04469.
Sidell
B D
BD
D000214:Acyl Coenzyme A / Q000378:metabolism*; D000818:Animals; D001110:Arctic Regions; D002469:Cell Separation; D002499:Centrifugation, Density Gradient; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D005399:Fishes; D008099:Liver / Q000378:metabolism*; D008830:Microbodies / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism*; D013379:Substrate Specificity
D000214:Acyl Coenzyme A; D005231:Fatty Acids, Unsaturated