Abstract
Aryl-alcohol oxidases (AAOs) are FAD-containing enzymes that oxidize a broad range of aromatic as well as aliphatic allylic alcohols to aldehydes. Their broad substrate spectrum accompanied by the only need for molecular oxygen as cosubstrate and production of hydrogen peroxide as sole by-product makes these enzymes very promising biocatalysts. AAOs were used in the synthesis of flavors, fragrances, and other high-value-added compounds and building blocks as well as in dye decolorization and pulp biobleaching. Furthermore, AAOs offer a huge potential as efficient suppliers of hydrogen peroxide for peroxidase- and peroxygenase-catalyzed reactions. A prerequisite for application as biocatalysts at larger scale is the production of AAOs in sufficient amounts. Heterologous expression of these predominantly fungal enzymes is, however, quite challenging. This review summarizes different approaches aiming at enhancing heterologous expression of AAOs and gives an update on substrates accepted by these promising enzymes as well as potential fields of their application.Key points• Aryl-alcohol oxidases (AAOs) supply ligninolytic peroxidases with H2O2.• AAOs accept a broad spectrum of aromatic and aliphatic allylic alcohols.• AAOs are potential biocatalysts for the production of high-value-added bio-based chemicals.
Highlights
Since decades, oxidoreductases have been recognized as valuable tools for synthetic chemistry, because they catalyze reactions that are often difficult or impossible to achieve with classical chemical catalysts (Hall 2020)
Their functions in nature and the general catalytic mechanism are considered deciphered, and the reactions catalyzed by Aryl-alcohol oxidases (AAOs) and summarized here impressively demonstrate the high potential of these enzymes for biotechnological purposes
Advances in protein engineering have prompted the construction of AAO variants with altered substrate scope and increased stereoselectivity, which opens new perspectives for synthetic chemistry
Summary
Oxidoreductases have been recognized as valuable tools for synthetic chemistry, because they catalyze reactions that are often difficult or impossible to achieve with classical chemical catalysts (Hall 2020). Oxidoreductases are of vital interest for developing the bioeconomy via efficient conversion of renewable feedstocks like lignocellulose to fuels and high-valueadded chemicals. White-rot fungi secrete a bunch of oxidative enzymes participating in the degradation of lignocellulosic biomass as a central step in carbon recycling. Since their discovery in 1960, significant knowledge has been gained with regard to structural, spectral, biochemical, and catalytic properties of fungal AAOs. Since their discovery in 1960, significant knowledge has been gained with regard to structural, spectral, biochemical, and catalytic properties of fungal AAOs All these achievements are a subject of several excellent reviews (Hernandez-Ortega et al 2012a; Serrano et al 2020) and will only be
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