The porphobilinogen deaminase encoded by the Clostridium josui hemC gene was purified from a recombinant Escherichia coli strain and its properties were characterized. The optimal temperature and pH of the purified enzyme were 65 degrees C and 7.0, respectively. This enzyme was quite thermostable: it retained 86% of the original activity after incubation at 70 degrees C for Ih. The K-m, and V-max values of the enzyme were 65 mu M and 3.3 mu mol/h/mg for porphobilinogen, respectively.