Polynucleotides encoding engineered ketoreductase polypeptides
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. The engineered ketoreductase polypeptides are optimized for catalyzing the conversion of N-methyl-3-keto-3-(2-thienyl)-1-propanamine to (S)—N-methyl-3-hydroxy-3-(2-thienyl)-1-propanamine.
1. An isolated or recombinant polynucleotide encoding a ketoreductase polypeptide, wherein the polypeptide has an amino acid sequence that is at least 90% identical to a reference sequence of SEQ ID NO:2 and has at least the following features: (a) the residue corresponding to residue X94 is aspartic acid, (b) the residue corresponding to residue X145 is phenylalanine; (c) the residue corresponding to residue X190 is proline, and (d) wherein the residue corresponding to X196 is a non-polar or aliphatic residue.
2. The polynucleotide of claim 1 , wherein the encoded amino acid sequence further comprises one or more features selected from the group consisting of:
residue corresponding to X40 is a constrained, hydrophilic or basic residue;
residue corresponding to X196 is a non polar or aliphatic residue;
residue corresponding to X226 is a non polar or aliphatic residue;
residue corresponding to X249 is a nonpolar or aromatic residue; and
wherein the amino acid sequence can optionally have one or more residue differences at other amino acid residues as compared to the reference sequence.
3. The polynucleotide of claim 1 , wherein the encoded amino acid sequence further comprises one or more of the following features:
residue corresponding to X40 is arginine;
residue corresponding to X226 is valine;
residue corresponding to X249 is tryptophan; and
wherein the amino acid sequence can optionally have one or more differences at other amino acid residues as compared to the reference sequence.
4. An expression vector comprising the polynucleotide of claim 1 operably linked to a control sequence suitable for directing expression in a host cell.
5. An isolated host cell comprising the expression vector of claim 4 .
6. The isolated host cell of claim 5 , wherein the host cell is E. coli.
7. The isolated host cell of claim 5 , wherein the polynucleotide comprises codons that have been optimized for expression in the host cell.
8. A method for preparing a ketoreductase polypeptide comprising expressing a polynucleotide of claim 1 in an isolated host cell and recovering the polypeptide from the host cell or culture medium.
9. The method of claim 8 , wherein the isolated host cell is E. coli.