Discovery of Two Native Baeyer-Villiger Monooxygenases for Asymmetric Synthesis of Bulky Chiral Sulfoxides

Abstract

Two Baeyer-Villiger monooxygenases (BVMOs), designated BVMO andBVMO, were discovered from and, respectively. Both monooxygenases displayed novel features for catalyzing the asymmetric sulfoxidation of bulky and pharmaceutically relevant thioethers. Evolutionary relationship and sequence analysis revealed that the two BVMOs belong to the family of typical type I BVMOs and the subtype ethionamide monooxygenase. Both BVMOs are active toward medium- and long-chain aliphatic ketones as well as various thioether substrates but are ineffective toward cyclohexanone, aromatic ketones, and other typical BVMO substrates. BVMO andBVMO showed the highest activities (0.117 and 0.025 U/mg protein, respectively) toward thioanisole among the tested substrates. Furthermore, these BVMOs exhibited distinct activity and excellent stereoselectivity toward bulky and prochiral prazole thioethers, which is a unique feature of this family of BVMOs. No native enzyme has been reported for the asymmetric sulfoxidation of bulky prazole thioethers into chiral sulfoxides. The identification of BVMO andBVMO provides an important scaffold for discovering enzymes capable of asymmetrically oxidizing bulky thioether substrates by genome mining. Baeyer-Villiger monooxygenases (BVMOs) are valuable enzyme catalysts that are an alternative to the chemical Baeyer-Villiger oxidation reaction. Although BVMOs display broad substrate ranges, no native enzymes were reported to have activity toward the asymmetric oxidation of bulky prazole-like thioether substrates. Herein, we report the discovery of two type I BVMOs from (BVMO) and (BVMO) which are able to catalyze the asymmetric sulfoxidation of bulky prazole thioethers (proton pump inhibitors [PPIs], a group of drugs whose main action is a pronounced and long-lasting reduction of gastric acid production). Efficient catalysis of omeprazole oxidation by BVMO was developed, indicating that this enzyme is a promising biocatalyst for the synthesis of bulky and pharmaceutically relevant chiral sulfoxide drugs. These results demonstrate that the newly identified enzymes are suitable templates for the discovery of more and better thioether-converting BVMOs.

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“…Baeyer–Villiger monooxygenases (BVMOs, EC 1.14.13.X) are the flavoenzymes which catalyze the electrophilic oxygenation of various heteroatoms and also insertion of an oxygen atom between a C–C bond in ketones and aldehydes which is very similar to the chemical Baeyer–Villiger oxidation (Zhang et al 2018). BVMOs are known to play a pivotal role in the degradation of ketones, steroid and metabolism of terpenoids.…”

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“…Importantly, no sulfone formation was observed. In addition, the BVMOs used exhibited pronounced activity and excellent stereoselectivity in relation to prochiral prazole thioethers, such as omeprazoles, ilaprazoles, rabeprazoles, pantoprazoles, and lansoprazoles, which is a unique feature in this BVMO family [75].…”

“…Importantly, no sulfone formation was observed. In addition, the BVMOs used exhibited pronounced activity and excellent stereoselectivity in relation to prochiral prazole thioethers, such as omeprazoles, ilaprazoles, rabeprazoles, pantoprazoles, and lansoprazoles, which is a unique feature in this BVMO family [75]. It was noted that Baeyer-Villiger Monooxygenases (BVMOs) from many microbes are sequentially associated with human FMO and exhibit similar effects; hence, they can be used as a tool to prepare metabolites in studies on the metabolism of xenobiotics [73].…”

Identification two key residues at the intersection of domains of a thioether monooxygenase for improving its sulfoxidation performance

“…Acinetobacter calcoaceticus shows 69.8% sequence identity with Ac-CHMO a . AcCHMO M6 is an AcCHMO b mutant we obtained previously that oxidizes OPS to the S-enantiomer of omeprazole (esomeprazole; Schema 1; Zhang et al, 2018Zhang et al, , 2019. Esomeprazole is the best-selling proton pump inhibitor for treating gastroesophageal reflux disease (Scott et al, 2002).…”