Catalyzes the sequential decarboxylation of the four acetate side chains of uroporphyrinogen to form coproporphyrinogen and participates in the fifth step in the heme biosynthetic pathway (PubMed:14633982, PubMed:11069625, PubMed:21668429, PubMed:11719352). Isomer I or isomer III of uroporphyrinogen may serve as substrate, but only coproporphyrinogen III can ultimately be converted to heme (PubMed:14633982, PubMed:11069625, PubMed:21668429, PubMed:11719352). In vitro also decarboxylates pentacarboxylate porphyrinogen I (PubMed:12071824). 4 H(+) + uroporphyrinogen III = 4 CO2 + coproporphyrinogen III 4 H(+) + uroporphyrinogen I = 4 CO2 + coproporphyrinogen I Porphyrin-containing compound metabolism; protoporphyrin-IX biosynthesis; coproporphyrinogen-III from 5-aminolevulinate: step 4/4. Homodimer. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the uroporphyrinogen decarboxylase family. Uroporphyrinogen III decarboxylase entry