Porphyrinogens which are intermediates in the heme biosynthesis. They have four methyl and four propionic acid side chains attached to the pyrrole rings. coproporphyrinogens I and III are formed in the presence of uroporphyrinogen decarboxylase from the corresponding uroporphyrinogen. They can yield coproporphyrins by autooxidation or protoporphyrin by oxidative decarboxylation.