Coproporphyrinogen III
Coproporphyrinogen III is a metabolic intermediate in the biosynthesis of many compounds that are critical for living organisms, such as hemoglobin and chlorophyll. It is a colorless solid.
The compound is a porphyrinogen, a class of compounds characterized by a hexahydroporphine core with various side chains. The coproporphyrinogens have the outermost hydrogen atoms of the core replaced by four methyl groups and four propionic acid groups . In coproporphyrogen III, the order around the outer ring is MP-MP-MP-PM. For comparison, coproporphyrinogen I has them in the sequence MP-MP-MP-MP. heme.In the main porphyrin biosynthesis pathway, coproporphyrinogen III is derived from uroporphyrinogen III by the action of the enzyme uroporphyrinogen III decarboxylase:
The conversion entails four decarboxylations, which turn the four acetic acid groups into methyl groups, with release of four carbon dioxide molecules.
Coproporphyrinogen III is further used as a substrate for the enzyme coproporphyrinogen III oxidase which oxidizes and further decarboxylates it to protoporphyrinogen IX.
