Purine nucleoside enzyme that catalyzes the phosphorolysis of adenosine and inosine nucleosides, yielding D-ribose 1-phosphate and the respective free bases, adenine and hypoxanthine (PubMed:31978345). Also catalyzes the phosphorolysis of S-methyl-5'-thioadenosine into adenine and S-methyl-5-thio-alpha-D-ribose 1-phosphate (PubMed:31978345). Also has adenosine deaminase activity (PubMed:31978345). adenosine + phosphate = adenine + alpha-D-ribose 1-phosphate phosphate + S-methyl-5'-thioadenosine = adenine + S-methyl-5-thio-alpha-D-ribose 1-phosphate inosine + phosphate = alpha-D-ribose 1-phosphate + hypoxanthine adenosine + H(+) + H2O = inosine + NH4(+) Binds 2 zinc ions (PubMed:31978345). One zinc is catalytic and mediates binding to the substrate, while the second is probably structural (PubMed:31978345). Belongs to the purine nucleoside phosphorylase YfiH/LACC1 family.