A novel 4-hydroxyacetophenone monooxygenase featuring aromatic substrates preference for enantioselective access to sulfoxides

Abstract

Baeyer-Villiger monooxygenases are recognized as valuable tools for biooxidative synthesis of chiral sulfoxides. In this work, a novel HAPMO ortholog from Pseudomonas fluorescens (HAPMOPf) was identified by genome mining. Evolutionary relationship and sequence analysis revealed that HAPMOPf belongs to the family of typical type I BVMOs. HAPMOPf has a low KM value (0.025 mM) toward 4-hydroxyacetophenone, and a half-life of 24 h at 30 °C and pH 9.0. HAPMOPf exhibited distinct activity toward aromatic ketones as well as various thioethers, such as methyl phenyl sulfide and bromo‑methyl phenyl sulfide. The highest activities of HAPMOPf was 1.47 U·mg−1 toward 4-hydroxyacetophenone among tested ketone and thioether substrates. Furthermore, over 95% enantioselectivity was determined toward methyl phenyl sulfides with ortho, meta, and para-substituents (Cl, Br, CHO, NH2). Therefore, HAPMOPf is a promising biocatalyst for the synthesis of aromatic esters and chiral sulfoxides.