( 2 ) guanosine is phosphorylitically cleaved to guanine and ribose-1-p by purine ribonucleoside phosphorylase ( purine-nucleoside : orthophosphate ribosyl transferase , ec 2.4.2.1 ) , present in d. discoideum extracts , and formycin b is a competitive inhibitor or this reaction with a very high affinity for the enzyme .
C0018330
guanosine
C0034136
purine-nucleoside