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

Baeyer-Villiger monooxygenases are recognized as valuable tools for biooxidative synthesis of chiral sulfoxides. In this work, a novel HAPMO ortholog from Pseudomonas fluorescens (HAPMO Pf ) was identified by genome mining. Evolutionary relationship and sequence analysis revealed that HAPMO Pf belongs to the family of typical type I BVMOs. HAPMO Pf has a low K M value (0.025 mM) toward 4-hydroxyacetophenone, and a half-life of 24 h at 30 °C and pH 9.0. HAPMO Pf 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 HAPMO Pf 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, NH 2 ). Therefore, HAPMO Pf is a promising biocatalyst for the synthesis of aromatic esters and chiral sulfoxides.