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• Acetyl CoA is formed by the enzymes pyruvate-formatelyase and pyruvate dehydrogenase.
• It enters as a substrate into the citric acid cycle to produce energy during aerobic respiration.

Pyruvate derived from glycolysis undergoes oxidative decarboxylation to create acetyl-CoA, releasing CO₂ and forming NADH in the process. Pyruvate dehydrogenase catalyzes this process. This is a redox reaction. The proton from NADH then travels to the electron transport chain, where it is used to make ATP.

The conversion of pyruvate to acetyl CoA in photosynthetic organisms is more complex. Instead of pyruvate dehydrogenase, they use pyruvate-formatelyase.

$\text{Pyruvate + HSCoA}⇌\text{acetyl - CoA + formate}$

Formate is generated in this reaction, but not CO₂ . There is no NADH generated in this reaction because this is not a redox reaction. Thus, no ATP is produced as a result of this reaction.