Purification and characterization of purine nucleoside phosphorylase and pyrimidine nucleoside phosphorylase from Bacillus stearothermophilus TH 6-2.

The purine nucleoside phosphorylase (Pu-NPase) and the pyrimidine nucleoside phosphorylase (Py-NPase) have been purified from Bacillus stearothermophilus TH 6-2. The Pu-NPase is a trimer of 30-kDa subunits and the Py-NPase is a dimer of 46-kDa subunits. The isoelectric points of Pu-NPase and Py-NPase were pH 4.3 and 4.6, respectively. The Pu-NPase could catalyze the phosphorolysis of inosine and guanosine, but not adenosine. the Py-NPase could phosphorolyze both uridine and thymidine.