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 (By similarity). Also catalyzes the phosphorolysis of S-methyl-5'-thioadenosine into adenine and S-methyl-5-thio-alpha-D-ribose 1-phosphate (By similarity). Also has adenosine deaminase activity (By similarity). Also acts as a multicopper oxidase able to oxidize a wide variety of polyphenols and related compounds in vitro (PubMed:16740638). Displays substrate preference as follows: syringaldazine > 2,6-dimethoxyphenol > veratryl alcohol > guaiacol > tetramethylbenzidine > 4-methoxybenzyl alcohol > 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) >> phenol red > 1-hydroxybenzotriazole (PubMed:16740638). Cannot use 3,4-dimetoxybenzyl alcohol and violuric acid as substrates (PubMed:16740638). As this enzyme is derived from a rumen microbial community, it may have a role in the digestion of complex plant materials such as ryegrass lignin (PubMed:16740638). 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 4 Cu cations per subunit. kcat is 18 sec(-1) with 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid as substrate. kcat is 660 sec(-1) with syringaldazine as substrate. kcat is 1175 sec(-1) with 2,6-dimethoxyphenol as substrate (at pH 4.5 and 40 degrees Celsius). Optimum pH is 4.0-5.0. Activity is very high over a broad pH range from 4.0 to 9.0. Exhibits more than 70% activity at pH 3.5 and 9.5. Optimum temperature is about 60 degrees Celsius. Is fully stable at this temperature. Homodimer. Belongs to the purine nucleoside phosphorylase YfiH/LACC1 family.