Catalyzes the reversible 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:235429). Acts on 6-amino and 6-oxopurines including deoxyinosine, deoxyguanosine, deoxyadenosine, adenosine, guanosine, and inosine (PubMed:235429). a purine D-ribonucleoside + phosphate = a purine nucleobase + alpha-D-ribose 1-phosphate a purine 2'-deoxy-D-ribonucleoside + phosphate = 2-deoxy-alpha-D-ribose 1-phosphate + a purine nucleobase inosine + phosphate = alpha-D-ribose 1-phosphate + hypoxanthine adenosine + phosphate = adenine + alpha-D-ribose 1-phosphate guanosine + phosphate = alpha-D-ribose 1-phosphate + guanine 2'-deoxyadenosine + phosphate = 2-deoxy-alpha-D-ribose 1-phosphate + adenine 2'-deoxyguanosine + phosphate = 2-deoxy-alpha-D-ribose 1-phosphate + guanine 2'-deoxyinosine + phosphate = 2-deoxy-alpha-D-ribose 1-phosphate + hypoxanthine Homohexamer; trimer of homodimers. Belongs to the PNP/UDP phosphorylase family.