2enoylCoA

2-enoyl-CoA, commonly referred to as trans-Δ2-enoyl-CoA, is a thioester formed between coenzyme A and a fatty acyl chain that contains a carbon–carbon double bond between the second and third carbon atoms (the Δ2 position). In biological contexts the double bond is typically in the trans geometry. This molecule is a key intermediate in fatty acid metabolism, particularly in the beta-oxidation pathway.

Chemical structure and naming: 2-enoyl-CoA denotes an acyl-CoA with a double bond at the position between C2 and C3 of the fatty acyl chain. The CoA moiety links to the fatty acyl skeleton via a thioester bond. The physiologically relevant form is usually trans-Δ2-enoyl-CoA, which serves as the substrate for subsequent hydration steps.

Role in metabolism: In beta-oxidation, saturated acyl-CoAs are dehydrogenated by acyl-CoA dehydrogenases to form trans-Δ2-enoyl-CoA. For fatty acids that enter oxidation with a cis-Δ3 double bond, an enoyl-CoA isomerase can convert cis-Δ3 into trans-Δ2-enoyl-CoA, enabling the oxidation cycle to proceed. The next step is hydration of trans-Δ2-enoyl-CoA by enoyl-CoA hydratase to yield a 3-hydroxyacyl-CoA, which is then dehydrogenated to a β-ketoacyl-CoA and continued in the cycle.

Biological significance and notes: 2-enoyl-CoA species are essential intermediates in energy production from fatty acids. Their formation and turnover are coupled to mitochondrial fatty acid oxidation and, in some cases, to peroxisomal pathways. Defects in enzymes handling enoyl-CoA intermediates can disrupt beta-oxidation and contribute to metabolic disorders, though specific clinical conditions depend on the involved enzyme and chain length.