The conversion of PEP to pyruvate mediated by pyruvate kinase is another key metabolic
step in the glycolytic pathway and is irreversible. Pyruvate is used in several metabolic
reactions. During respiration, pyruvate is further converted to acetyl coenzyme A (acetyl
CoA), which enters the citric acid cycle through which it is completely oxidized to carbon
dioxide (Fig. 3.3). The conversion of pyruvate to acetyl CoA is mediated by the enzyme
complex pyruvate dehydrogenase and is an oxidative step that involves the formation of
NADH from NAD. Acetyl CoA is a key metabolite and starting