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 lead poisoning, there is an inhibition of some of the enzymes of the heme biosynthetic pathway. This is reflected by the accumulation of what substance in blood? 
Select and explain. 
A. Uroporphyrinogen III, B. Ferrochelatase, C. Porphob I inogen, D. Delta amino levulinic acid
D: Delta amino levulinic acid
Answer: D: Delta amino levulinic acid 
Explanation: Ans: D. Delta amino levulinic acid(Ref: Harper 30/e n329)Lead poisoning:Affect heme metabolism by combining with SH groups in ferrochelatase & ALA (delta-amino levulinic acid) dehydratase enzymes.Elevated protoporphyrin levels - Found in RBC's.Elevated ALA & coproporphyrin levels - Found in urine.