Affiliation:
1. UFZ Centre for Environmental Research Leipzig-Halle, D-06120 Halle
2. Biotype Gesellschaft für Molekularbiologische Analytik AG, D-01109 Dresden, Germany
Abstract
ABSTRACT
A purified and electrophoretically homogeneous blue laccase from the litter-decaying basidiomycete
Stropharia rugosoannulata
with a molecular mass of approximately 66 kDa oxidized Mn
2+
to Mn
3+
, as assessed in the presence of the Mn chelators oxalate, malonate, and pyrophosphate. At rate-saturating concentrations (100 mM) of these chelators and at pH 5.0, Mn
3+
complexes were produced at 0.15, 0.05, and 0.10 μmol/min/mg of protein, respectively. Concomitantly, application of oxalate and malonate, but not pyrophosphate, led to H
2
O
2
formation and tetranitromethane (TNM) reduction indicative for the presence of superoxide anion radical. Employing oxalate, H
2
O
2
production, and TNM reduction significantly exceeded those found for malonate. Evidence is provided that, in the presence of oxalate or malonate, laccase reactions involve enzyme-catalyzed Mn
2+
oxidation and abiotic decomposition of these organic chelators by the resulting Mn
3+
, which leads to formation of superoxide and its subsequent reduction to H
2
O
2
. A partially purified manganese peroxidase (MnP) from the same organism did not produce Mn
3+
complexes in assays containing 1 mM Mn
2+
and 100 mM oxalate or malonate, but omitting an additional H
2
O
2
source. However, addition of laccase initiated MnP reactions. The results are in support of a physiological role of laccase-catalyzed Mn
2+
oxidation in providing H
2
O
2
for extracellular oxidation reactions and demonstrate a novel type of laccase-MnP cooperation relevant to biodegradation of lignin and xenobiotics.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
176 articles.
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