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. It can use NAD or NADP, but NAD is preferred. 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. Inhibited by EDTA. Porphyrin-containing compound metabolism; protoporphyrin-IX biosynthesis; protoporphyrinogen-IX from coproporphyrinogen-III (AdoMet route): step 1/1. Monomer. The structure carries two S-adenosyl-L-methionine binding sites with only one binding to the iron-sulfur cluster. Belongs to the anaerobic coproporphyrinogen-III oxidase family. Extended N-terminus.