This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
All are components of Citric acid cycle EXCEPT: 
Select and explain. 
A. Fumarase, B. Malonate, C. Succinate dehydrogenase, D. Alpha-ketoglutarate dehydrogenase
B: Malonate
Answer: B: Malonate 
Explanation: Malonate competitively inhibits succinate dehydrogenase, which conves succinate to fumarate