The use of white rot fungi such as Pleurotus ostreatus and their lignin-modifying enzymes has become an effective treatment for various organic soil and water pollutants. The manganese peroxidase gene family (mnps) is a major part of the ligninolytic system of P. ostreatus. This gene family is comprised nine genes encoding short manganese peroxidases (short-MnPs) or versatile peroxidases (VPs). The exposed active site on the VPs surface is responsible of direct oxidation (in the absence of Mn2+) of high and low potential redox aromatic compounds. We show that unlike in Mn2+-amended glucose-peptone (GP) medium, where redundancy among mnps was reported, in Mn2+-deficient GP medium vp1 (encoding VP1) has a key and non-redundant function. We used the azo-dye Orange II (OII) as a model contaminate, its decolorization occurs only during the idiophase where the abundance transcripts of mnps indicate that vp1 is the predominantly expressed and a Δvp1 strain showed a drastic reduction in this decolorization. Three degradation metabolites were identified by LC-MS indicating both asymmetric and symmetric enzymatic cleavage of the azo bond. The presence of asymmetric cleavage diminishes the toxicity level of the degradation products. In addition, the culture filtrate of Δvp1 showed negligible values of oxidation capability of four typical VP substrates compared to the wild type strain. To better understand mechanisms of degradation and detoxification we purified and characterized VP1. The purified enzyme degraded 50% of OII within 5 min and within 30 min the degradation continued up until 95%. The non-specific oxidation properties of VP1 demonstrate its potential application for treatment of contaminated water.
