Question
A 22-year-old Caucasian female with recurrent abdominal pain and anxiety has had marked improvement in her symptoms after intravenous administration of a heme preparation. Rapid improvement of symptoms in this patient is most likely due to significant repression of:
| A. |
δ-Aminolevulinate synthase |
| B. |
δ-Aminolevulinate dehydratase |
| C. |
Hydroxymethylbilane synthase |
| D. |
Ferrochelatase |
Show Answer
|
Correct Answer � A Explanation |
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Ans. A δ-Aminolevulinate synthase
Explanation: Decreased heme concentration results in an increase in hepatic ALA synthase activity, which in turn, leads to increased formation of δ-aminolevulinic acid and porphobilinogen. Increased formation of o-aminolevulinic acid and porphobilinogen occurs because heme normally serves to inhibit the synthesis of ALA synthase.