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:
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.