Arbutin oxidation by pear (Pyrus communis L.) peroxidases

The oxidation of arbutin (hydroquinone-beta-D-glucopyranoside) by soluble and ionically bound to cell wall peroxidases (EC. 1.11.1.7) from pear (Pyrus communis L.) shoots is described for the first time. Following the initiation of the reaction with hydrogen peroxide, arbutin was transformed to a product that was detected by UV spectrophotometry. The stoichiometry of the oxidized product formation versus hydrogen peroxide was nearly 2:1 suggesting that arbutin oxidation is a one-electron process. Higher oxidation rates were observed in a narrow pH zone and ionically bound peroxidases showed lower apparent K-m for arbutin than soluble ones. Arbutin is considered to be an antioxidant and peroxidases from pear may influence the pro- or antioxidant properties of this compound. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.