Methods of using engineered ketoreductase polypeptides for the stereoselective reduction of acetophenones
The present disclosure provides engineered ketoreductase enzymes having improved properties as compared to a naturally occurring wild-type ketoreductase enzyme. Also provided are polynucleotides encoding the engineered ketoreductase enzymes, host cells capable of expressing the engineered ketoreductase enzymes, and methods of using the engineered ketoreductase enzymes to synthesize a variety of chiral compounds.
1. A method for stereoselectively reducing a 2′,6′-substituted acetophenone substrate, optionally substituted at one or more positions selected from the group consisting of 3′, 4′, and 5′, to the corresponding substituted (S)-1-phenethanol, which comprises contacting the substrate with an engineered ketoreductase polypeptide under reaction conditions suitable for stereoselectively reducing or converting the substrate to the corresponding substituted (S)-1-phenethanol product, wherein the engineered ketoreductase polypeptide: (a) comprises an amino acid sequence at least 90% identical to the reference sequence of SEQ ID NO: 2, 4, or 98; (b) comprises an alanine, proline, or cysteine residue at a position corresponding to position 190 of SEQ ID NO: 2, 4, or 98; and (c) is capable of stereoselectively reducing acetophenone to (S)-1-phenethanol.
2. The method of claim 1 , wherein the substrate is 2′,6′-dichloro-3′-fluoroacetophenone and the corresponding substituted (S)-1-phenethanol product is (S)-1-(2,6-dichloro-3-fluorophenyl)ethanol.
3. The method of claim 2 , wherein the (S)-1-(2,6-dichloro-3-fluorophenyl)ethanol is formed in greater than 99% stereomeric excess.
4. The method of claim 1 , wherein at least 95% of the substrate is reduced to the product in less than 24 hours when the method is conducted with at least 200 g/L of substrate and with less than 2 g/L of the polypeptide.
5. The method of claim 1 , wherein the method is carried out with whole cells that express the engineered ketoreductase polypeptide, or an extract or lysate of such cells.
6. The method of claim 1 , wherein the engineered ketoreductase polypeptide is isolated and/or purified and the reduction reaction is carried out in the presence of a cofactor for the ketoreductase.
7. The method of claim 6 , wherein the reduction reaction is carried out in the presence of a regeneration system for the cofactor.
8. The method of claim 7 , in which the cofactor regenerating system comprises glucose dehydrogenase and glucose; formate dehydrogenase and formate; or isopropanol and a secondary alcohol dehydrogenase.
9. The method of claim 8 , wherein the secondary alcohol dehydrogenase is the ketoreductase.
10. The method of claim 1 , wherein the amino acid sequence has a proline at a position corresponding to position 190 of SEQ ID NO: 2, 4, or 98.