You learned about the aptly named enzyme Citrate Synthase. There are more enzymes that count citrate as substrate or product. Co
mpare and contrast two reactions below that each split two carbons from citrate to make oxaloacetate. One catalyzed by the enzyme ATP Citrate Lyase and the second catalyzed by Citrate Lyase. Acetyl-CoA
Citrate → ↑ → Oxaloacetate lyase
CoA-SH → ↑ ↑ ←ATP ↓→ ADP + Pi
ATP Citrate
Acetate
Citrate → ↑ ↓→ Oxaloacetate
Citrate lyase
Which of the following is an accurate statement about why ATP is required by ATP Citrate Lyase?
a) The hydrolysis of the thioester involving CoA-SH helps split ATP into ADP and Pi.
b) The hydrolysis of ATP helps "pay for the formation of a thioester involving CoA-SH.
c) The Acetyl-CoA is pulled rapidly away to make lipids so the reaction needs extra energy to make it fast enough to keep up with demand.
d) The two carbons of acetate are more energetic than those on Acetyl-CoA and therefore don't need ATP to split them from citrate.
e) ATP is required to spit the two carbons from citrate.
b) The hydrolysis of ATP helps "pay for the formation of a thioester involving CoA-SH.
Explanation:
In the citrate cycle, we know that lysis is mediated by the hydrolysis of ATP, which is the fuel of the reaction, so the correct answer is B. The hydrolysis of ATP helps "pay for the formation of a thioester involving CoA-SH.
