The Laccase of Myrothecium roridum VKM F‐3565: A New Look at Fungal Laccase Tolerance to Neutral and Alkaline Conditions**

Abstract

Most of the currently known fungal laccases show their maximum activity under acidic environmental conditions. It is known that a decrease in the activity of a typical laccase at neutral or alkaline pH values is the result of an increase in the binding of the hydroxide anion to the T2/T3 copper center, which prevents the transfer of an electron from the T1 Cu to the trinuclear copper center. However, evolutionary pressure has resolved the existing limitations in the catalytic mechanism of laccase, allowing such enzymes to be functionally active under neutral/alkaline pH conditions, thereby giving fungi an advantage for their survival. Combined molecular and biochemical studies, homological modeling, calculation of the electrostatic potential on the Connolly surface at pH 5.0 and 7.0, and structural analysis of the novel alkaliphilic laccase of Myrothecium roridum VKM F‐3565 and alkaliphilic and acidophilic fungal laccases with a known structure allowed a new intramolecular channel near the one of the catalytic aspartate residues at T2‐copper atom to be found. The amino acid residues of alkaliphilic laccases forming this channel can presumably serve as proton donors for catalytic aspartates under neutral conditions, thus ensuring proper functioning. For the first time for ascomycetous laccases, the production of new trimeric products of phenylpropanoid condensation under neutral conditions has been shown, which could have a potential for use in pharmacology.

Food-Grade Expression of Two Laccases in Pichia pastoris and Study on Their Enzymatic Degradation Characteristics for Mycotoxins

“…Conventional detoxification methods for mycotoxins involve physical, chemical, and microbial approaches. , However, these methods possess drawbacks such as nutrient loss, reagent residues, and secondary pollution to the environment. , In contrast, enzymatic degradation offers advantages, including mild reaction conditions, high efficiency, low cost, and convenient operations. , Fungal laccases (EC 1.10.32) have attracted considerable attention due to their environmentally friendly characteristics and catalytic properties, such as high oxidation–reduction potentials, wide temperature ranges, and maximum activity under acidic conditions. , These characteristics make them suitable for use in food and feed environments . To date, several studies have reported the efficiency of laccases from fungi and bacteria in degrading AFB 1 and ZEN.…”

“…17,18 These characteristics make them suitable for use in food and feed environments. 18 To date, several studies have reported the efficiency of laccases from fungi and bacteria in degrading AFB 1 and ZEN. Zhao et al reported that Bacillus licheniformis laccase CotA was able to degrade 39% of the AFB 1 and 70% of the ZEN.…”

“…15,16 Fungal laccases (EC 1.10.32) have attracted considerable attention due to their environmentally friendly characteristics and catalytic properties, such as high oxidation−reduction potentials, wide temperature ranges, and maximum activity under acidic conditions. 17,18 These characteristics make them suitable for use in food and feed environments. 18 To date, several studies have reported the efficiency of laccases from fungi and bacteria in degrading AFB 1 and ZEN.…”

Unusual Oligomeric Laccase-like Oxidases from Ascomycete Curvularia geniculata VKM F-3561 Polymerizing Phenylpropanoids and Phenolic Compounds under Neutral Environmental Conditions

“…Recently, our team has found fungi producing oxidases that are the most active in relation to phenolic compounds and phenylpropanoids under slightly alkaline environmental conditions (at pH 7.0-9.0): Rhizoctonia solani VKM F-895, Myrothecium verrucaria VKM F-3851, Myrothecium roridum VKM F-3565, and C. geniculata VKM F-3561 [26,27]. Alkaliphilic laccase of the fungus M. roridum VKM F-3565 was isolated and characterized [28]. A novel proton channel has been observed in its molecule as well as in molecules of known alkaliphilic fungal laccases, which provide the transfer of protons to the T2/T3-copper cluster necessary for functional activity of the enzyme under neutral and alkaline environments [28].…”

“…Alkaliphilic laccase of the fungus M. roridum VKM F-3565 was isolated and characterized [28]. A novel proton channel has been observed in its molecule as well as in molecules of known alkaliphilic fungal laccases, which provide the transfer of protons to the T2/T3-copper cluster necessary for functional activity of the enzyme under neutral and alkaline environments [28].…”