Uroporphyrinogen Decarboxylase (UROD)

URODencodes the fifth enzyme of the heme biosynthetic pathway. This enzyme is responsible for catalyzing the conversion of uroporphyrinogen to coproporphyrinogen through the removal of four carboxymethyl side chains.Uroporphyrinogen III decarboxylase (UroD) is a homodimeric enzyme which 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. 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. The enzyme functions as a dimer in solution, and both the enzymes from human and tobacco have been crystallized and solved at good resolutions.