A 3-year-old child presents with a history of recurrent rash upon sun exposure and passage of purple-colored urine. The child is diagnosed with congenital erythropoietic porphyria (CEP), a disorder associated with the pathway of heme biosynthesis. Which of the following intermediates of TCA cycle is used as a precursor for heme biosynthesis?
A) acetyl-CoA
B) malate
C) pyruvate
D) succinate
E) succinyl-CoA

Question

Quizplus · Accepted Answer

Succinyl-CoA is an intermediate of the TCA cycle that combines with glycine to form delta-aminolevulinic acid (ALA), the first step in heme biosynthesis.  The initiation of heme biosynthesis requires glycine and the TCA cycle intermediate, succinyl-CoA.

A 3-Year-Old Child Presents with a History of Recurrent Rash