What is the primary action of citrate synthase in the citric acid cycle?

Citrate synthase plays a crucial role in the citric acid cycle by catalyzing the conversion of oxaloacetate to citrate. This reaction is the first step in the cycle and marks the beginning of a series of metabolic transformations that ultimately lead to energy production.

The activity of citrate synthase involves the condensation of oxaloacetate and acetyl-CoA to form citrate. This is a key regulatory step in the cycle, as it initiates the sequence of reactions that follow. The formation of citrate is significant because it also signifies the entry of acetyl-CoA, derived from carbohydrates, fats, or proteins, into the cycle for oxidative degradation.

This reaction is a pivotal point for the cycle, as citrate then undergoes various transformations to eventually regenerate oxaloacetate, thus allowing the cycle to continue. The function of citrate synthase in this context highlights the importance of integrating various metabolic pathways and fuels into ATP production.