cis3enoylCoA

cis-3-enoyl-CoA, or cis-3-enoyl-CoA thioester, is a CoA thioester of a fatty acyl chain that contains a cis double bond between the third and fourth carbon atoms counting from the carboxyl end. It represents an intermediate in the beta-oxidation pathway of unsaturated fatty acids.

In standard beta-oxidation, the required double bond for the enoyl-CoA hydratase step is in the trans-2 position. When a substrate carries a cis-3 double bond, enoyl-CoA isomerase catalyzes the rearrangement of cis-3-enoyl-CoA to trans-2-enoyl-CoA, enabling subsequent steps of oxidation, hydration, and thiolysis to proceed. In mammals, the enzyme responsible is enoyl-CoA isomerase (EC 5.3.3.8; often associated with mitochondrial or peroxisomal localization, depending on tissue and substrate). For more complex polyunsaturated fatty acids, additional enzymes such as 2,4-dienoyl-CoA reductase may participate to process multiple double bonds before final beta-oxidation.

cis-3-enoyl-CoA can arise transiently during the catabolism of certain dietary unsaturated fatty acids and is typically converted rapidly to trans-2-enoyl-CoA as part of normal fatty acid degradation. Its management is part of the broader network of enzymes that adapt beta-oxidation to unsaturated substrates.

See also: beta-oxidation, enoyl-CoA isomerase, 2,4-dienoyl-CoA reductase, unsaturated fatty acids metabolism.