During beta-oxidation of polyunsaturated fatty acids, what reducing agent is utilized?

In the process of beta-oxidation of polyunsaturated fatty acids, the reducing agent utilized is NADPH. Beta-oxidation is primarily responsible for breaking down fatty acids into acetyl-CoA units, and this process involves several enzymatic reactions.

During the oxidation of polyunsaturated fatty acids, additional cycles of reduction and isomerization occur to accommodate the presence of double bonds. The unsaturated bonds in polyunsaturated fatty acids require specific enzymes, such as enoyl-CoA isomerase and 2,4-dienoyl-CoA reductase, for proper processing. These reactions generate NADPH, which assists in reducing the bonds appropriately for subsequent oxidation steps.

In contrast, the other agents mentioned play distinct roles: FADH2 and NADH are produced during other steps of beta-oxidation involving saturated fatty acids, serving as electron carriers for the electron transport chain. CoA is a critical cofactor required for the activation of fatty acids before they undergo beta-oxidation but is not classified as a reducing agent. Therefore, NADPH is specifically the reducing agent needed for processing polyunsaturated fatty acids during these additional enzymatic steps in beta-oxidation.