Volume 215, number 2, 228-232 FEB 04659 May 1987 /?-oxidation of polyunsaturated fatty acids in peroxisomes Subcellular distribution of 43,42-enoyl-CoA isomerase activity in rat liver T. Klrki*, E. Hakkola*, I.E. Hassinen* and J.K. Hiltunen*+ Departments of *Medical Biochemistry and ‘Clinical Chemistry, University of Oulu. Kajaanintie 52A, SF-90220 Oulu, Finland Received 26 February 1987 The metabolism of the double bonds at the A3 position in fatty acids was studied in rat liver. Infusion of A3-trans-dodecenoic acid into isolated perfused liver and subcellular fractionation studies showed the pres- ence of both peroxisomal and mitochondrial A3,A2-enoyl-CoA isomerase activity (EC 5.3.3.8). These find- ings together with the previous demonstration of peroxisomal 2,Cdienoyl-CoA reductase (EC 1.3.1.34) [(1981) J. Biol. Chem. 256, 8259-82621 and D-3-OH-acyl-CoA epimerase (EC 5.1.2.3) [(1985) FEBS Lett. 185, 129-1341 activities show that peroxisomes possess all the auxiliary enzymes required for the 8-oxidation of unsaturated fatty acids. Polyunsaturated fatty acid; Peroxisome; Catalase compound I; Organ spectroscopy; (Rat liver) 1. INTRODUCTION Very-long-chain fatty acids accumulate in pa- tients with deficient peroxisomal &oxidation as a consequence of an inherited disease [l-4]. This fact together with the in vitro characteristics of peroxisomal P-oxidation indicates that the physiological task of this metabolic process is the catabolism of long-chain fatty acids [5]. Long- chain fatty acids in nature are often unsaturated, however, and are usually degraded only slowly in mitochondria. Many polyunsaturated fatty acids (PUFA) are even inhibitors of mitochondrial fi- oxidation [6]. The first indication that peroxisomes may be specifically involved in the metabolism of PUFA emerged from the demonstration of the existence of peroxisomal 2,Cdienoyl-CoA reductase in rat Correspondence address: J.K.Hiltunen, Dept of Medical Biochemistry, University of Oulu, Kajaanintie 52 A, SF-90220 Oulu, Finland liver [7]. Similarly, 3-OH-acyl-CoA epimerase ap- pears to be a peroxisomal enzyme [8]. The third auxiliary enzyme involved in the & oxidation of unsaturated fatty acids is A3,A2-enoyl- CoA isomerase, which catalyzes the isomerization of the double bond in position 3 of acyl-CoA derivatives to position 2. As a step towards the understanding of the role of peroxisomes in the catabolism of unsaturated fatty acids, it is necessary to know whether they can metabolize double bonds at odd-numbered positions in fatty acids. This prompted us to study the subcellular distribution of this isomerase activity in the liver. 2. MATERIALS AND METHODS The fatty acids used were all commercially available, except for A3-trans-dodecenoic acid, which was synthesized by condensing decyl aldehyde with malonic acid in the presence of triethanolamine [9]. The acyl-CoA esters were syn- thesized by the mixed anhydride method [lo] and 228 Published by Elsevier Science Publishers B. V. (Biomedical Division) 00145793/87/$3.50 0 1987 Federation of European Biochemical Societies brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Elsevier - Publisher Connector