Mechanisms and physiological roles of fatty acid chain elongation in microsomes and mitochondria.

Abstract

1. The characterization and separation of two enoyl-CoA reductases from rat liver with different catalytic properties are described. 2. Studies on the subcellular location revealed both enzymes to be constituents of a mitochondrial and microsomal fatty acid chain elongation system, respectively. 3. The microsomal enzyme shows optimal activity with hexenoyl-CoA, the mitochondrial enoyl-CoA reductase with decenoyl-CoA. The implications of this observation regarding a preference for γ-linolenic acid and linolenic acid, respectively, as the physiological substrates of microsomal and mitochondrial enoyl-CoA reductase will be discussed. 4. The mitochondrial enoyl-CoA reductases from rat liver and heart exhibit different pyridine nucleotide specificities. The implications of these differences concerning important roles in gluconeogenesis or nitrogen metabolism and in conservation of energy, respectively, is discussed. 5. A possible relationship between mitochondrial fatty acid chain elongation in the aorta and the pathogenesis of atherosclerosis is discussed.