Abstract: The present disclosure provides MTR kinase polypeptides having improved properties as compared to a naturally occurring wild-type MTR kinase polypeptide including the capability of phosphorylating D-ribose and 5?-D-isobutyrylribose to give alpha-D-ribose-1-phosphate and alpha 5?-D-isobutyrylribose-1-phosphate. Also provided are polynucleotides encoding the MTR kinase polypeptides, host cells capable of expressing the MTR kinase polypeptides, and methods of using the MTR kinase polypeptides to synthesize alpha-D-ribose-1-phosphate and alpha 5?-D-isobutyrylribose-1-phosphate.

Abstract: The present disclosure provides ketoreductase enzymes having improved properties as compared to a naturally occurring wild-type ketoreductase enzyme including the capability of reducing N-(7-((2S,4R,5R)-4-fluoro-3,3-dihydroxy-5-(hydroxymethyl) tetrahydrofuran-2-yl)-4-oxo-4,7-dihydro-3H-pyrrolo[3,2-d]pyrimidin-2-yl)isobutyramide. Also provided are polynucleotides encoding the ketoreductase enzymes, host cells capable of expressing the ketoreductase enzymes, and methods of using the ketoreductase enzymes to synthesize N-(9-((2R,3S,4S,5R)-4-fluoro-3-hydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)-6-oxo-6,9-dihydro-1H-purin-2-yl)isobutyramide.

Abstract: The present invention discloses a serum-free medium for full suspension culture of MDCK cells and a preparation method of the serum-free medium. The serum-free medium for full suspension culture of the MDCK cells comprises basic metabolic nutrients, nucleotide, vitamins, inorganic salts, a shear force protective agent, a cell clustering resisting agent, a pH buffer agent, a pH indicator, an influenza virus proliferation accelerant and other additives. The preparation method of the serum-free medium for the full suspension culture of the MDCK cells comprises the following steps: 1) preparing a mixed solution: dissolving and mixing raw materials; and 2) regulating pH: regulating the pH of the mixed solution to 6.3 to 6.7, and setting a constant volume to obtain the serum-free medium for the full suspension culture of the MDCK cells.