Two purine nucleoside phosphorylases in Bacillus subtilis. Purification and some properties of the adenosine-specific phosphorylase.

Two purine nucleoside phosphorylases (purine-nucleoside:orthophosphate ribosyltransferase, EC 2.4.2.1) were purified from vegetative Bacillus subtilis cells. One enzyme, inosine-guanosine phosphorylase, showed great similarity to the homologous enzyme of Bacillus cereus. It appeared to be a tetramer of molecular weight 95 000. The other enzyme, adenosine phosphorylase, was specific for adenosine and deoxyadenosine. The molecular weight of the native enzyme was 153 000 +/- 10% and the molecular weight of the subunits was 25 500 +/- 5%. This indicates a hexameric structure. The adenosine phosphorylase was inactivated by 10(-3) M p-chloromercuribenzoate and protected against this inactivation by phosphate, adenosine and ribose 1-phosphate.