Pyruvate Oxidation (Link Reaction)

The two molecules of pyruvate produced by glycolysis in the cytosol must first cross into the mitochondrial matrix before aerobic respiration can continue. There, each pyruvate is oxidatively decarboxylated -- combined with coenzyme A while losing a carbon as CO2 -- to form acetyl coenzyme-A (acetyl CoA), a reaction catalysed by the pyruvate dehydrogenase complex and driven by Mg2+. This step is irreversible, and because it forms the chemical bridge connecting glycolysis to the Krebs cycle, it is also called the transition or link reaction. Each pyruvate oxidised yields one $NADH + H^+$ and releases one CO2, so the reaction for both pyruvates together is $2\,CH_3COCOOH + 2NAD^+ + 2CoA \rightarrow 2\,CH_3CO{\cdot}CoA + 2NADH + 2H^+ + 2CO_2\uparrow$. The pyruvate dehydrogenase complex itself is a large multi-enzyme assembly made of three distinct enzymes -- pyruvate dehydrogenase, dihydro …