Coproporphyrinogen Oxidase (CPOX)

Coproporphyrinogen III oxidase is the sixth enzyme of the heme biosynthetic pathway. The encoded enzyme is soluble and found in the intermembrane space of mitochondria. This enzyme catalyzes the stepwise oxidative decarboxylation of coproporphyrinogen III to protoporphyrinogen IX, a precursor of heme. The gene spans about 14 kb and consists of 7 exons and 6 introns. Introns vary in size from 269 bp to 5 kb and all have consensus sequences at their boundaries. This fragment was used as a hybridization probe to isolate full-length CPO clones from a mouse erythroleukemia cell cDNA library. Sequence analysis demonstrated that CPO comprises 354 amino acid residues with a putative leader sequence of 31 amino acid residues, the mature protein having 323 amino acid residues.