Uroporphyrinogen decarboxylase (UROD), is an enzyme of the heme biosynthetic pathway which belongs to the uroporphyrinogen decarboxylase family. This enzyme is responsible for catalyzing the conversion of uroporphyrinogen to coproporphyrinogen through the removal of four carboxymethyl side chains. UROD is a homodimeric enzyme that catalyzes the fifth step in heme biosynthesis: the elimination of carboxyl groups from the four acetate side chains of uroporphyrinogen III to yield coproporphyrinogen III. Defects in UROD are the cause of familial porphyria cutanea tarda (FPCT) and hepatoerythropoietic porphyria (HEP).