In the presence of saturating amounts of oxaloacetate, the activity of citrate synthase from pig heart tissue shows a sigmoid dependence on the concentration of acetyl-CoA. When succinyl-CoA is added, the curve shifts to the right and the sigmoid dependence is more pronounced. Choose the statements that are reasonable explanations for the right-ward shift of the velocity curve caused by succinyl-CoA. Succinyl-CoA binds at a regulatory site other than the active site. Succinyl-CoA competes with oxaloacetate for binding at the active site. Succinyl-CoA competes with dissociation of CoA as a product of the reaction. Succinyl-CoA binds covalently to the enzyme. ☐ Succinyl-CoA competes with acetyl-CoA for binding at the active site. Activity (% of Vmax) 100F No 80- 60- 40- 20- succinyl-CoA D Succinyl-CoA added 20 40 60 80 100 120 [Acetyl-CoA] (µM) Citrate synthase is regulated by another metabolite that has the opposite effect (i.e., stimulates citrate synthase). Choose the description of a condition where a positive regulator activates citrate synthase. High [citrate]. Citrate is a positive allosteric activator. High [NADH/NAD+] ratio. NADH is a positive allosteric activator. ☐ High [ATP/ADP] ratio. High ATP substrate levels favor product formation. Low [ATP/ADP] ratio. ADP is an allosteric activator of citrate synthase.