1JPH, 1JPI, 1JPK, 1R3Q, 1R3R, 1R3S, 1R3T, 1R3V, 1R3W, 1R3Y, 1URO, 2Q6Z, 2Q71, 3GVQ, 3GVR, 3GVV, 3GVW, 3GW0, 3GW3738922275ENSG00000126088ENSMUSG00000028684P06132P70697NM_000374NM_009478NP_000365NP_033504Uroporphyrinogen III decarboxylase (uroporphyrinogen decarboxylase, or UROD) is an enzyme (EC 4.1.1.37) that in humans is encoded by the UROD gene.

[5] Uroporphyrinogen III decarboxylase is a homodimeric enzyme (PDB: 1URO​) that catalyzes the fifth step in heme biosynthesis, which corresponds to the elimination of carboxyl groups from the four acetate side chains of uroporphyrinogen III to yield coproporphyrinogen III: Mutations and deficiency in this enzyme are known to cause familial porphyria cutanea tarda and hepatoerythropoietic porphyria.

[6] At low substrate concentrations, the reaction is believed to follow an ordered route, with the sequential removal of CO2 from the D, A, B, and C rings, whereas at higher substrate/enzyme levels a random route seems to be operative.

UroD is regarded as an unusual decarboxylase, since it performs decarboxylations without the intervention of any cofactors, unlike the vast majority of decarboxylases.

Its mechanism has recently been proposed to proceed through substrate protonation by an arginine residue.