Purification and Reaction of a New Enzyme, Nucleoside Oxidase

Nucleoside oxidase, a novel nucleoside oxidizing enzyme has been purified from a crude extract of Pseudomonas maltophilia LB-86 by a ammonium sulfate fractionation, heat treatment, column chromatography on DEAE-Toyopearl, and gel filtration twice on Sephacryl S-200. The overall purification was approximately 60-fold with a yield of 35 %. The purified enzyme gave a single protein band on acrylamide gel electrophoresis. Reaction products from inosine were identified as inosine-5′-aldehyde and inosine-5′-carboxylic acid. The enzyme catalyzed the oxidation of inosine to inosine-5′-carboxylic acid via inosine-5′-aldehyde using molecular oxygen as a primary electron acceptor with no formation of hydrogen peroxide.