Characterization of the inorganic pyrophosphatase from the pathogenic bacterium Helicobacter pylori

Abstract.

A cytoplasmic pyrophosphatase [E.C. 3.6.1.1.] was partially purified from Helicobacter pylori. The molecular mass was estimated to be 103 kDa by gel filtration. Results of SDS-PAGE suggested that the enzyme consists of six identical subunits of 19.1 kDa each. The enzyme specifically catalyzed the hydrolysis of pyrophosphate and was very sensitive to NaF, but not to sodium molybdate. The optimal pH for activity was 8.5. Mg²⁺ was required for maximal activity; Mn²⁺, Co²⁺, and Zn²⁺ poorly supported hydrolytic activity. The pyrophosphatase had an apparent K _m for Mg-PP_i ^2– hydrolysis of 90 µM, and a V _max estimated at 24.0 µmol P_i min^–1 mg^–1.