This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Medicine
Enzyme defect in acute intermittent porphyria 
Select and explain. 
A. PMB deaminase, B. ALA dehydratase, C. UROI synthase, D. URO II synthase
A: PMB deaminase
Answer: A: PMB deaminase 
Explanation: Ref - Davidsons 23e p378