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Fig. 1. The critical role of acetyl-CoA in oxidative metabolism. Both glucose and fatty acids yield acetyl-CoA which can enter the tricarboxylic acid cycle for complete oxidation. Pyruvate generated by glycolysis (
) from glucose generates acetyl-CoA via pyruvate dehydrogenase (
). If acetyl-CoA generation exceeds utilization in the tricarboxylic acid cycle, acetyl-CoA will accumulate and can inhibit pyruvate dehydrogenase ( – – – in figure). Pyruvate will be converted to lactate if pyruvate dehydrogenase activity is inadequate. The removal of the acetyl group as acetylcarnitine via carnitine acetyltransferase (
) can remove this inhibition and produce an alternative product of oxidation. The net production of acetylcarnitine can only be sustained for very brief periods in human muscle.
