Biocatalysis with Laccases: An Updated Overview

Ivan Bassanini,Daniela Monti,Erica Elisa Ferrandi,Sergio Riva

doi:10.3390/catal11010026

Abstract

Laccases are multicopper oxidases, which have been widely investigated in recent decades thanks to their ability to oxidize organic substrates to the corresponding radicals while producing water at the expense of molecular oxygen. Besides their successful (bio)technological applications, for example, in textile, petrochemical, and detoxifications/bioremediations industrial processes, their synthetic potentialities for the mild and green preparation or selective modification of fine chemicals are of outstanding value in biocatalyzed organic synthesis. Accordingly, this review is focused on reporting and rationalizing some of the most recent and interesting synthetic exploitations of laccases. Applications of the so-called laccase-mediator system (LMS) for alcohol oxidation are discussed with a focus on carbohydrate chemistry and natural products modification as well as on bio- and chemo-integrated processes. The laccase-catalyzed Csp2-H bonds activation via monoelectronic oxidation is also discussed by reporting examples of enzymatic C-C and C-O radical homo- and hetero-couplings, as well as of aromatic nucleophilic substitutions of hydroquinones or quinoids. Finally, the laccase-initiated domino/cascade synthesis of valuable aromatic (hetero)cycles, elegant strategies widely documented in the literature across more than three decades, is also presented.

Highlights

Applications of the so-called laccase-mediator system (LMS) for alcohol oxidation are discussed with a focus on carbohydrate chemistry and natural products modification as well as on bio- and chemo-integrated processes
The laccase-catalyzed Csp2-H bonds activation via monoelectronic oxidation is discussed by reporting examples of enzymatic C-C and C-O radical homo- and hetero-couplings, as well as of aromatic nucleophilic substitutions of hydroquinones or quinoids
Laccases are enzymes belonging to the blue multicopper oxidase family that catalyze the oxidation of a wide range of substrates, such as phenols and aromatic or aliphatic amines, thereby reducing molecular oxygen to water

Summary

Introduction

Laccases are enzymes belonging to the blue multicopper oxidase family that catalyze the oxidation of a wide range of substrates, such as phenols and aromatic or aliphatic amines, thereby reducing molecular oxygen to water. Most of them are monomeric, some have been reported to be homodimeric, heterodimeric, and multimeric, with molecular mass ranging from 50 to 140 kDa, including their sugar component Their amino acid sequence could span from 220 to 800 amino acids and may contain 2 or 3 cupredoxin-like domains depending on the organism they belong to. In fungi these biocatalysts are involved in lignin degradation, in plants are key in the lignification process and cell wall formation [5], while in insects they seem to participate in the sclerotization of the cuticle [7] Both the possibility to use laccases in synthetic or degradative processes and their wide substrate specificity make these enzymes suitable “green tools” for a plethora of applications in different fields, such as textile, paper, food, pharmaceutical and cosmetics [6,8]. We will describe the numerous reaction outcomes that can derive from their catalytic action

Laccases Catalytic Cycle and Their Use in Non-Conventional Reaction Systems

Findings

Conclusions and Perspectives