title: beta-Oxidation of polyunsaturated fatty acids by rat liver peroxisomes. A role for 2,4-dienoyl-coenzyme A reductase in peroxisomal beta-oxidation.
abstract: beta-Oxidation of unsaturated fatty acids was studied with isolated solubilized or nonsolubilized peroxisomes or with perfused liver isolated from rats treated with clofibrate. gamma-Linolenic acid gave the higher rate of beta-oxidation, while arachidonic acid gave the slower rate of beta-oxidation. Other polyunsaturated fatty acids (including docosahexaenoic acid) were oxidized at rates which were similar to, or higher than, that observed with oleic acid. Experiments with 1-14C-labeled polyunsaturated fatty acids demonstrated that these are chain-shortened when incubated with nonsolubilized peroxisomes. Spectrophotometric investigation of solubilized peroxisomal incubations showed that 2,4-dienoyl-CoA esters accumulated during peroxisomal beta-oxidation of fatty acids possessing double bond(s) at even-numbered carbon atoms. beta-Oxidation of [1-14C]docosahexaenoic acid by isolated peroxisomes was markedly stimulated by added NADPH or isocitrate. This fatty acid also failed to cause acyl-CoA-dependent NADH generation with conditions of assay which facilitate this using other acyl-CoA esters. These findings suggest that 2,4-dienoyl-CoA reductase participation is essential during peroxisomal beta-oxidation if chain shortening is to proceed beyond a delta 4 double bond. Evidence obtained using arachidionoyl-CoA, [1-14C]arachidonic acid, and [5,6,8,9,11,12,14,15-3H]arachidonic acid suggests that peroxisomal beta-oxidation also can proceed beyond a double bond positioned at an odd-numbered carbon atom. Experiments with isolated perfused livers showed that polyunsaturated fatty acids also in the intact liver are substrates for peroxisomal beta-oxidation, as judged by increased levels of the catalase-H2O2 complex on infusion of polyunsaturated fatty acids.
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D007700:Kinetics; D008042:Linolenic Acids / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008830:Microbodies / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism; D010084:Oxidation-Reduction; D044925:Oxidoreductases Acting on CH-CH Group Donors; D051381:Rats; D017962:alpha-Linolenic Acid
chemical_list: D000214:Acyl Coenzyme A; D001095:Arachidonic Acids; D005231:Fatty Acids, Unsaturated; D008042:Linolenic Acids; D017962:alpha-Linolenic Acid; D016718:Arachidonic Acid; D044943:Fatty Acid Desaturases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C100153:2,4-dienoyl-CoA reductase