This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymes, Subject name: Biochemistry
Ferrochelatase is inhibited by - 
Select and explain. 
A. Arsenic, B. Lead, C. Chromium, D. Mercury
B: Lead
Answer: B: Lead 
Explanation: Ans. is 'b' i.e., Lead * Lead inhibits ALA dehydratase. Therefore, lead poisoning causes inhibition of heme synthesis and excessive amount of d-ALA is excreted in urine. Lead can also inhibit ferrochelatase (heme synthase).