Open AccessOxidation of hydroquinones by the versatile ligninolytic peroxidase from Pleurotus eryngii
Author(s) -
GómezToribio Víctor,
Martínez Angel T.,
Martínez María J.,
Guillén Francisco
Publication year - 2001
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2001.02405.x
Subject(s) - chemistry , hydroquinone , autoxidation , semiquinone , peroxidase , pleurotus eryngii , quinone , hydrogen peroxide , radical , pyrogallol , oxalate , redox , catechol , peroxide , horseradish peroxidase , nuclear chemistry , organic chemistry , enzyme , raw material
Formation of H 2 O 2 during the oxidation of three lignin‐derived hydroquinones by the ligninolytic versatile peroxidase (VP), produced by the white‐rot fungus Pleurotus eryngii , was investigated. VP can oxidize a wide variety of phenols, including hydroquinones, either directly in a manner similar to horseradish peroxidase (HRP), or indirectly through Mn 3+ formed from Mn 2+ oxidation, in a manner similar to manganese peroxidase (MnP). From several possible buffers (all pH 5), tartrate buffer was selected to study the oxidation of hydroquinones as it did not support the Mn 2+ ‐mediated activity of VP in the absence of exogenous H 2 O 2 (unlike glyoxylate and oxalate buffers). In the absence of Mn 2+ , efficient hydroquinone oxidation by VP was dependent on exogenous H 2 O 2 . Under these conditions, semiquinone radicals produced by VP autoxidized to a certain extent producing superoxide anion radical ( – ) that spontaneously dismutated to H 2 O 2 and O 2 . The use of this peroxide by VP produced quinone in an amount greater than equimolar to the initial H 2 O 2 (a quinone/H 2 O 2 molar ratio of 1 was only observed under anaerobic conditions). In the presence of Mn 2+ , exogenous H 2 O 2 was not required for complete oxidation of hydroquinone by VP. Reaction blanks lacking VP revealed H 2 O 2 production due to a slow conversion of hydroquinone into semiquinone radicals (probably via autooxidation catalysed by trace amounts of free metal ions), followed by – production through semiquinone autooxidation and – reduction by Mn 2+ . This peroxide was used by VP to oxidize hydroquinone that was mainly carried out through Mn 2+ oxidation. By comparing the activity of VP to that of MnP and HRP, it was found that the ability of VP and MnP to oxidize Mn 2+ greatly increased hydroquinone oxidation efficiency.