Selective oxidation of alkyl and aryl glyceryl monoethers catalysed by an engineered and immobilised glycerol dehydrogenase

• Published in: Chemical science (Cambridge) Vol. 11; no. 44; pp. 129 - 122
• Main Authors: Velasco-Lozano, Susana, Roca, Maite, Leal-Duaso, Alejandro, Mayoral, José A, Pires, Elisabet, Moliner, Vicent, López-Gallego, Fernando
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 05-10-2020; The Royal Society of Chemistry
• Subjects: Aromatic compounds; Chemistry; Dehydrogenases; Enantiomers; Enzymes; Ethanol; Ethers; Glycerol; Isomers; Mutation; Oxidation
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d0sc04471g

Enzymes acting over glyceryl ethers are scarce in living cells, and consequently biocatalytic transformations of these molecules are rare despite their interest for industrial chemistry. In this work, we have engineered and immobilised a glycerol dehydrogenase from
Bacillus stearothermophilus
(BsGlyDH) to accept a battery of alkyl/aryl glyceryl monoethers and catalyse their enantioselective oxidation to yield the corresponding 3-alkoxy/aryloxy-1-hydroxyacetones. QM/MM computational studies decipher the key role of D123 in the oxidation catalytic mechanism, and reveal that this enzyme is highly enantioselective towards
S
-isomers (ee > 99%). Through structure-guided site-selective mutagenesis, we find that the mutation L252A sculpts the active site to accommodate a productive configuration of 3-monoalkyl glycerols. This mutation enhances the
k
cat
163-fold towards 3-ethoxypropan-1,2-diol, resulting in a specific activity similar to the one found for the wild-type towards glycerol. Furthermore, we immobilised the L252A variant to intensify the process, demonstrating the reusability and increasing the operational stability of the resulting heterogeneous biocatalyst. Finally, we manage to integrate this immobilised enzyme into a one-pot chemoenzymatic process to convert glycidol and ethanol into 3-ethoxy-1-hydroxyacetone and (
R
)-3-ethoxypropan-1,2-diol, without affecting the oxidation activity. These results thus expand the uses of engineered glycerol dehydrogenases in applied biocatalysis for the kinetic resolution of glycerol ethers and the manufacturing of substituted hydroxyacetones.
Design and fabrication of a robust heterogeneous biocatalyts for the selective oxidation of alkyl/aryl glyceryl monoethers through the engineering and immobilization of glycerol dehydrogenases.