Combination of Substrate Engineering, Medium Engineering and Immobilization Technique to Improve Enzyme Performances in Hydrolytic Resolution Processes

In the past two years, we have found that Klebsiella oxytoca esterase from Nagase & Co. Ltd has excellent enantioselectivity for the hydrolytic resolution of (R,S)-ethyl 2-chloromandelate. When further investigating the leaving alcohol moiety effects on the enzyme performance, a maximum enantioselectivity was obtained. The results have induced our motivation to carry out the project, in which we would testify if the previous kinetic model is also valid to other substrates, and verify a hypothesis proposed herein on improving the enzyme enantioselectivity. In the following three years, the research topic will be focused on “combination of substrate engineering, medium engineering and immobilization technique to improve enzyme performances in hydrolytic resolution processes,” in which several chiral 2-hydroxy carboxylic acids and 3-hydroxy carboxylic acids as important intermediates for drug or agrochemical synthesis are regarded as target products. In the first year, effects of acyl and leaving alcohol moieties of the (R,S)-2-hydroxy carboxylic acid ester on the enzyme performance at an optimal medium condition will be studied, and the kinetic model previously proposed for (R,S)-ethyl 2-chloromandelate verified. In the second year, an immobilization technique with multipoint covalent attachment to modify the neutral and cationic amino acid residues on enzyme surface is proposed such that the pKA of triad histidine is manipulated to improve the enzyme enantioselectivity and recovery. In the third year, the analysis will be extended to (R,S)-3-hydroxy carboxylic acid esters. The results will be compared with those for (R,S)-2-hydroxy carboxylic acid esters, from which the enzyme specificity on enantioselectivity can be obtained when varying the substrate structure.

Project ID:PB9902-0661
External Project ID:NSC97-2221-E182-018-MY3