How Pyruvate Is Converted to Acetyl-CoA

The citric acid cycle takes place in the mitochondrial matrix, with exception that one enzyme is located in the inner mitochondrial membrane. The closely related process of oxidative phosphorylation takes place in the inner mitochondrial membrane. 

How many enzymes are needed to convert pyruvate to acetyl-CoA  

Lipoic acid differs in one respect from other coenzymes. It is a vitamin, rather than a metabolite of a vitamin, as is the case with many other coenzymes (Table 7.3). (The classification of lipoic acid as a vitamin is open to question. There 

A second advantage of a multienzyme complex is that regulatory controls can be applied more efficiently in such a system than in a single enzyme molecule. In the case of the pyruvate dehydrogenase complex, controlling factors are intimately associated with the multienzyme complex itself, which we shall study in Section 19.5. 

The two-carbon unit needed at the start of the citric acid cycle is obtained by converting pyruvate to acetyl-GoA. 

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How many enzymes are needed to convert pyruvate to acetyl-CoA Pyruvate is produced by glycolysis in the cytosol of the cell. The citric acid cycle takes place in the matrix of the mitochondria, so the pyruvate must first pass through a transporter into this organelle. There, pyruvate will find pyruvate dehydrogenase, a large, multisubunit protein made up of three enzymes involved in the production of acetyl-GoA plus two enzyme activities involved in control of the enzymes. The reaction requires several cofactors, including FAD, Upoic acid, and TPP. 

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