Question

In the citric acid cycle when an aldol addition occurs in a biological system, how do the amino acids contained in the Citrate Synthase enzyme help facilitate the reaction

Answer 1

Citrate Synthase facilitates the formation of citrate by deprotonating Acetyl CoA and by protonating the carbonyl oxygen of oxaloacetate

Step-by-step explanation:

Citrate synthase is a key enzyme in the citric acid cycle that functions to catalyze the formation of citrate from oxaloacetate and acetyl-CoA: acetyl-CoA + oxaloacetate + H2O >> citrate + CoA-SH (Coenzyme A ). This enzyme contains three amino acids at its active site that work together to catalyze the conversion of acetyl-CoA and oxaloacetate into citrate. This active site acts by abstracting (deprotonating) a proton from the alpha carbon of Acetyl CoA which serves as the nucleophile. Subsequently, the active site of the enzyme also protonates the carbonyl oxygen of oxaloacetate, which then suffers nucleophilic attack and thereby facilitating nucleophilic substitution reaction.