Affiliation:
1. Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
2. Department of Biotechnology, Israel Institute for Biological Research, Ness-Ziona, Israel
Abstract
ABSTRACT
Although Mn
2+
is the most abundant substrate of versatile peroxidases (VPs), repression of
Pleurotus ostreatus
vp1
expression occurred in Mn
2+
-sufficient medium. This seems to be a biological contradiction. The aim of this study was to explore the mechanism of direct oxidation by VP1 under Mn
2+
-deficient conditions, as it was found to be the predominant enzyme during fungal growth in the presence of synthetic and natural substrates. The native VP1 was purified and characterized using three substrates, Mn
2+
, Orange II (OII), and Reactive Black 5 (RB5), each oxidized by a different active site in the enzyme. While the pH optimum for Mn
2+
oxidation is 5, the optimum pH for direct oxidation of both dyes was found to be 3. Indeed, effective
in vivo
decolorization occurred in media without addition of Mn
2+
only under acidic conditions. We have determined that Mn
2+
inhibits
in vitro
the direct oxidation of both OII and RB5 while RB5 stabilizes both Mn
2+
and OII oxidation. Furthermore, OII was found to inhibit the oxidation of both Mn
2+
and RB5. In addition, we could demonstrate that VP1 can cleave OII in two different modes. Under Mn
2+
-mediated oxidation conditions, VP1 was able to cleave the azo bond only in asymmetric mode, while under the optimum conditions for direct oxidation (absence of Mn
2+
at pH 3) both symmetric and asymmetric cleavages occurred. We concluded that the oxidation mechanism of aromatic compounds by VP1 is controlled by Mn
2+
and pH levels both in the growth medium and in the reaction mixture.
IMPORTANCE
VP1 is a member of the ligninolytic heme peroxidase gene family of the white rot fungus
Pleurotus ostreatus
and plays a fundamental role in biodegradation. This enzyme exhibits a versatile nature, as it can oxidize different substrates under altered environmental conditions. VPs are highly interesting enzymes due to the fact that they contain unique active sites that are responsible for direct oxidation of various aromatic compounds, including lignin, in addition to the well-known Mn
2+
binding active site. This study demonstrates the limits of versatility of
P. ostreatus
VP1, which harbors multiple active sites, exhibiting a broad range of enzymatic activities, but they perform differently under distinct conditions. The versatility of
P. ostreatus
and its enzymes is an advantageous factor in the fungal ability to adapt to changing environments. This trait expands the possibilities for the potential utilization of
P. ostreatus
and other white rot fungi.
Funder
Israel Science Foundation
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
38 articles.
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