Studies on the metabolism of unsaturated fatty acids. XIII. Properties of 2,4-dienoyl-CoA reductase from beef liver.

It is demonstrated that 3-alkenoyl-CoA is the product of the enzymic reduction catalyzed by 2,4-dienoyl-CoA reductase with the highly purified enzyme preparation from beef liver mitochondria. Incorporation of deuterium atoms from deuterium-labeled NADPH and 2H2O during the reaction catalyzed by 2,4-dienoyl-CoA reductase from beef liver was investigated. When trans-2, trans-4-decadienoyl-CoA was incubated with the reductase in the presence of 4R-[4-2H1]NADPH and H2O, no deuterium was detected in the reaction product by gas chromatography-mass spectrometry after derivatization to pyrrolidine amides of fatty acids. When the substrate was incubated with the enzyme in the presence of 4S-[4-2H1]NADPH and H2O, one deuterium atom was incorporated into the product, 3-decenoate, at the C-5 position. In the case of 3-decenoate enzymatically prepared in the presence of NADPH and 2H2O, two deuterium atoms were incorporated into the product at the C-2 position. These results indicate that the reaction catalyzed by 2,4-dienoyl-CoA reductase from beef liver is a unique example of 1,4-addition of hydrogen to a 1,3-diene system conjugated with a carbonyl group of a thioester in biochemical fields. Chain length specificity of the reductase, isotope effects on reaction rates and competitive inhibitors are also discussed.