Peroxygenase-catalysed oxyfunctionalisation reactions.

Abstract

Peroxygenases represent a class of versatile heme-thiolate enzymes capable of catalysing highly selective oxyfunctionalisation reactions, particularly the hydroxylation of non-activated C-H bonds. This transformation, which poses substantial challenges in conventional organic synthesis, underscores the potential of peroxygenases in green chemistry applications. While cytochrome P450 monooxygenases have long been the primary focus for such biocatalytic transformations, their industrial adoption has been limited due to complex electron transfer chains and cofactor requirements. In contrast, peroxygenases bypass these limitations by directly utilising hydrogen peroxide (H₂O₂) to activate the catalytic heme site, thereby circumventing the oxygen dilemma typically encountered in P450 catalysis. Key milestones in peroxygenase research include the identification of chloroperoxidase from Caldariomyces fumago and the subsequent discovery of unspecific peroxygenases, such as those from Agrocybe aegerita, which exhibit broad substrate specificity and high catalytic efficiency. Here, we explore the mechanistic pathway of peroxygenase-catalysed reactions, emphasising the formation and decay of Compound I and the catalytic cycle's various functional outcomes. Critical aspects such as in situ H₂O₂ generation to mitigate enzyme inactivation, substrate loading strategies for practical applications, and the role of enzyme and reaction engineering in enhancing regio- and stereoselectivity are examined. Additionally, we address challenges in reaction scalability and operational stability for preparative-scale applications, offering insights into innovative protocols involving immobilised enzymes and non-aqueous reaction media. This review highlights recent advancements in the peroxygenase field and underscores the enzyme's promising role in sustainable oxyfunctionalisation reactions.