Crystallization and preliminary X-ray diffraction studies of E. coli porphobilinogen synthase and its heavy-atom derivatives.

Porphobilinogen synthase (PBGS) catalyzes the condensation of two identical substrate molecules, 5-aminolevulinic acid (ALA), in an asymmetric manner to form porphobilinogen. E. coli PBGS is an homooctameric enzyme.