Involved in the heme 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. By the redox response regulator Anr under aerobic and anaerobic conditions and by Dnr only under anaerobic conditions. Cells lacking this gene accumulate coproporphyrinogen-III both under aerobic and anaerobic conditions, however they do not exhibit any obvious growth defects. The hemN hemF double mutant do not abolish aerobic and anaerobic respiratory growth. Belongs to the anaerobic coproporphyrinogen-III oxidase family.