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
Arsenic inhibits all except : 
Select and explain. 
A. PDH, B. Lipoic acid, C. a-KG dehydrogenase, D. Enolase
D: Enolase
Answer: D: Enolase 
Explanation: D i.e. EnolaseArsenite (trivalent form of arsenic) forms a stable complex with thiol (-SH) group of lipoic acid, making it unavailable to serve as a coenzyme. So arsenic poisoning is primarily d/t inhibition of enzymes that require lipoic acid (lipoate) as a coenzyme including E2 of PDH complex, a-Ketoglutarate dehydrogenase and branched chain a-ketoacid dehydrogenaseQ.