Question

which of the following statements about the mechanism of citrate synthase enzyme is tr ujj:! a) citryl coa binds to the active site causing a conformation change allowing the acctyl coa to bind to the enzyme. b) acetyl coa is the nucleophile that attacks the oxaloacetate electrophile. c) this reaction involves covalent catalysis between the enzyme and one of the substrates. d) the conformation change which allows h2o to bind to the active site occurs before the formation of the c-c bond. e) this reaction does not involve any general acid-base catalysis.

Answer 1

The correct statement about citrate synthase's mechanism is that acetyl CoA acts as a nucleophile to attack the electrophile oxaloacetate, leading to citrate formation in the Citric Acid Cycle.

Step-by-step explanation:

The correct answer to the question about the mechanism of the enzyme citrate synthase is: b) acetyl coa is the nucleophile that attacks the oxaloacetate electrophile. In the Citric Acid Cycle, the -CH3 group of acetyl-CoA is deprotonated, forming a carbanion, which is a strong nucleophile. This carbanion then attacks the electrophilic carbon of the ketone group in oxaloacetate, leading to the formation of citroyl-CoA. The enzyme catalyzes the nucleophilic addition reaction, which results in the citroyl-CoA intermediate that is hydrogen-bonded to a histidine residue on the enzyme, activating the thioester group for hydrolysis. This subsequent hydrolysis reaction releases citrate and coenzyme A (HS-CoA) from the enzyme.