Uroporphyrinogen decarboxylase (EC 4.1.1.37) (URO-D), the fifth enzyme of the heme biosynthetic pathway, catalyzes the sequential decarboxylation of the four acetyl side chains of uroporphyrinogen to yield coproporphyrinogen [1].

URO-D deficiency is responsible for the Human genetic diseases familial porphyria cutanea tarda (fPCT) and hepatoerythropoietic porphyria (HEP).

The sequence of URO-D has been well conserved throughout evolution. The best conserved region is located in the N-terminal section; it contains a highly conserved hexapeptide. There are two arginine residues in this hexapeptide which could be involved in the binding, via salt bridges, to the carboxyl groups of the propionate side chains of the substrate. We used this region as a signature pattern. A second signature pattern is based on a another well conserved region which is located in the central section of the protein.