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
In Citric acid cycle, which enzyme is inhibited by arsenite? 
Select and explain. 
A. Isocitrate Dehydrogenase, B. a ketoglutarate Dehydrogenase, C. Succinate Dehydrogenase, D. Aconitase
B: a ketoglutarate Dehydrogenase
Answer: B: a ketoglutarate Dehydrogenase 
Explanation: Ans. is 'b' i.e., a ketoglutarate DehydrogenaseArsenite binds to the sulfhydryl group and hence inhibits the activity of enzymes which have lipoamide in the active site, Hence Arsenite inhibits Pyruvate Dehydrogenase and a ketoglutarate dehydrogenase of citric acid cycle, It is an example for non competitive inhibition, Succinate dehydrogenase is inhibited by malonate.