Purification and characterization of a 4-hydroxybenzoate decarboxylase from Chlamydophila pneumoniae AR39

Chlamydophila pneumoniae AR39 is an obligate intracellular pathogen that causes human acute and chronic respiratory tract diseases. One protein from C. pneumoniae AR39 was assigned as 4-hydroxybenzoate decarboxylase (HBDC). Assays done with the purified oxygen-sensitive protein showed that the optimum pH and temperature were 7.5 and 30 degrees C, respectively. The Km and Vmax obtained for 4-hydroxybenzoate were approximately 0.21 mM and 11.9 nM min(-1) mg(-1), respectively. During the period of 4-hydroxybenzoate decarboxylation, overall activity of the thermal-sensitive protein was 5.06 nM min(-1) mg(-1) protein. The 4-hydroxybenzoate decarboxylation was promoted by Mg(2+), Fe(2+), Mn(2+), and Ca(2+) but not by Cu(2+) or Zn(2+). The enzyme also slowly catalyzed the reverse reaction, which was phenol carboxylation.