Involved in the heme and chlorophyll biosynthesis. Catalyzes the anaerobic oxidative decarboxylation of propionate groups of rings A and B of coproporphyrinogen III to yield the vinyl groups in protoporphyrinogen IX. coproporphyrinogen III + 2 S-adenosyl-L-methionine = 2 5'-deoxyadenosine + 2 CO2 + 2 L-methionine + protoporphyrinogen IX Binds 1 [4Fe-4S] cluster. The cluster is coordinated with 3 cysteines and an exchangeable S-adenosyl-L-methionine. Porphyrin-containing compound metabolism; protoporphyrin-IX biosynthesis; protoporphyrinogen-IX from coproporphyrinogen-III (AdoMet route): step 1/1. Monomer. Induced under microoxic conditions. Cells lacking this gene grow significantly slower than that of the wild-type under microoxic conditions, while they grow normally under aerobic conditions. Coproporphyrin-III is accumulated at a low but significant level in the mutant growing under microoxic conditions. Belongs to the anaerobic coproporphyrinogen-III oxidase family.