coproporphyrinogen

Coproporphyrinogen is an intermediate in the heme biosynthesis pathway in animals, plants, and many bacteria. It is produced from uroporphyrinogen III by the enzyme uroporphyrinogen decarboxylase, in a decarboxylation reaction that removes peripheral carboxyl groups to yield the tetrapyrrole coproporphyrinogen III. As a porphyrinogen, it is a colorless, non-aromatic precursor to the porphyrin compounds.

In most organisms, coproporphyrinogen III is transported into mitochondria, where coproporphyrinogen oxidase catalyzes its oxidation to protoporphyrinogen IX. This molecule is then oxidized to protoporphyrin IX, and finally iron is inserted by ferrochelatase to form heme.

An isomer, coproporphyrinogen I, is not used in canonical heme biosynthesis and is often discussed in comparative or diagnostic contexts. The physiologically relevant intermediate and product in humans and many organisms is the III isomer.

Clinical relevance: Partial deficiency of coproporphyrinogen oxidase leads to hereditary coproporphyria, a rare form of porphyria characterized by neurovisceral symptoms, abdominal pain, and photosensitivity in some patients. Diagnosis involves monitoring porphyrin precursors in urine, blood, and feces; management focuses on avoiding triggers and treating symptoms.

Properties: Porphyrinogens like coproporphyrinogen are typically colorless and more susceptible to oxidation than their porphyrin counterparts. They are intermediates in biosynthetic pathways rather than stable end products.