Catalyzes the phosphorolytic breakdown of the N-glycosidic bond in the beta-(deoxy)ribonucleoside molecules, with the formation of the corresponding free purine bases and pentose-1-phosphate (PubMed:23438750, PubMed:9305964). Preferentially acts on 6-oxopurine nucleosides including inosine and guanosine (PubMed:9305964).
