2) Oxidation of product by E2 utilizing Lipoamide & subsequent transfer of Acetyl group to CoA
*The hydroxyethyl carbanion on TPP of E1 reacts with the disulfide of lipoamide on E2. What was the keto carbon of pyruvate is oxidized to a carboxylic acid, as the disulfide of lipoamide is reduced to a dithiol. The acetate formed by oxidation of the hydroxyethyl moiety is linked to one of the thiols of the reduced lipoamide as a thioester (~).
*The acetate is transferred from the thiol of lipoamide to the thiol of coenzyme A, yielding acetyl CoA.
*The reduced lipoamide swings over to the E3 active site. Dihydrolipoamide is reoxidized to the disulfide, as 2 e- + 2 H+ are transferred to a disulfide on E3 (disulfide interchange).