Laccase-like activity of nucleoside oxidase in the presence of nucleosides.

Abstract

Nucleoside oxidase that was purified to an electrophretically homogeneousstate catalyzed the oxidation of hydroquinone only in the presence of nucleosides simultaneously with the oxidation of nucleosides. From the identification of the reaction products and a chemical balance study, we concluded that the oxidation of hydroquinone proceeded by the following scheme: 2 hydroquinone + O2->2p-quinone + 2H2O. The enzyme also catalyzed the oxidation of various phenolic compounds and strongly colored substances were formed from phenolic compoundswith 4-aminoantipyrine in proportion to the amountof nucleosides. As described in earlier communications,1~3) we found a new enzyme that catalyzes the oxidation of nucleosides to nucleoside-5'-carboxylic acid via nucleoside-5'-aldehyde without a requirement for an exogenous co factor. The enzymewas purified from the cell-free extract of Pseudomonas maltophilia LB-86 by a procedure involving column chromatographies on DEAE-Toyopearl and gel filtration on Sephacryl S-200. The final preparation was homogeneous on polyacrylamide gel electrophoresis. The purified enzyme oxidized various nucleosides but not did attack nucleotides, bases, or ribose. During the investigation on this enzyme, we found that the enzyme catalyzes the oxidation of hydroquinone to pquinone. This oxidation reaction was identical with that of laccase (EC 1.10.3.2), but this activity of nucleoside oxidase appeared only in the presence of nucleoside. This paper describes an identification of the reaction product and the stoichiometry of enzyme reaction using hydroquinone as a substrate. The activities against various phenolic compoundsand the coupling reaction of phenolic compounds and 4-aminoantipyrine are also presented.

Laccases and their occurrence in prokaryotes

“…A nucleoside oxidase, which exhibits laccase-like activity in the presence of nucleosides, has been found in a strain of Pseudomonas mal- (Isono and Hoshino 1989). The first convincing data for a prokaryotic laccase activity were presented for Azospirillum lipoferum (Givaudan et al 1993).…”

A New Colorimetric Measurement of Fish Freshness Using Nucleoside Oxidase

“…At the same time, the enzyme catalyzed the oxidative coupling reaction of phenolic compounds and 4-aminoantipyrine to form colored substances, as with laccase (EC 1.10.3.2), and the amount of colored substances formed is proportional to the amount of nucleosides oxidized. 14 ) This phenomenon was used for estimation of the concentrations ofnucleosides, such as HxR and adenosine. IMP is hydrolyzed to HxR by alkaline phosphatase (EC 3.1.3.1), and Hx is also converted to HxR by nucleoside phosphorylase (EC 2.4.2.1) in the presence of ribose-1-phosphate.…”

Nucleoside Oxidase, a Hydrogen Peroxide-Forming Oxidase, from Flavobacterium meningosepticum

“…Only one enzyme, nucleoside oxidase (EC 1.1.3.28), has been reported to catalyze oxidation of nucleosides. The enzyme from Pseudomonas maltophilia (3)(4)(5)(6) catalyzes the oxidation of nucleosides to the corresponding nucleoside-5Ј-carboxylic acid via nucleoside-5Јaldehyde, using molecular oxygen as a primary electron acceptor, without formation of hydrogen peroxide. The enzyme also shows laccase-like activity in the presence of nucleosides (6).…”