Purification and Properties of Nucleoside Hydrolase from Pseudomonas jhorescens*

An enzyme which catalyzes the hydrolytic cleavage of various ribonucleosides to free base and ribose components has been obtained from cells of Pseudomonas fluorescens and purified about 300-fold by fractionation with protamine sulfate, ammonium sulfate, alumina Cy, and diethylaminoethyl cellulose. The preparation thus purEed catalyzes the hydrolysis of about 50 moles of uridine per min per mg of protein at 37”, and is stable when stored at -15”. The enzyme is highly specik for nucleosides containing the @-D-ribofuranosyl carbon-nitrogen linkage. A broad specificity is shown with respect to the base components: both pyrimidine and purine ribonucleosides are hydrolyzed. Because the maximum rate of hydrolysis of a pyrimidine nudeoside is generally much greater than that of a purine nucleoside, the systematic name N-ribosylpyrimidine ribodydrolase is suggested for this enzyme.