Abstract: The preparation method for a polypeptide includes the steps of constructing an engineering strain for fusion-expressing a polypeptide gene with a Sumo tag, and inducing the engineering strain for the soluble expression of a polypeptide, obtaining a crude protein containing a polypeptide precursor from the engineering strain by purification, cleaving the crude protein containing the polypeptide precursor by a Ulp1 protease to remove the Sumo tag, and purifying a cleavage product of the Ulp1 protease by a method of acetonitrile combined with heating precipitation or a method of precipitation with hexafluoro isopropanol to obtain the polypeptide.

Abstract: Provided is a ketoreductase mutant and applications thereof. Compared with an amino acid sequence shown in SEQ ID NO: 1, the amino acid sequence of the ketoreductase mutant includes at least one of the following mutation sites: L198P, S96W/I/L/V, M194L or L1526, herein “/” means “or.” The ketoreductase mutant provides high selectivity and high activity with respect to a substrate ketone, and the application of the mutant in a catalytic reduction reaction of a ketone substrate may increase the production efficiency of a chiral alcohol compound corresponding thereto.

Abstract: An amino acid sequence of the transaminase mutant is an amino acid sequence obtained by a mutation of an amino acid sequence is shown in SEQ ID NO: 1. The mutation occurred at least one of the following mutation sites: G17V, L36P, Q40H, G69Y, H70T, L73A, V77G, V77S, V77T, A78I, Y130M, Y130V, Y130T, N132I, N132T, K141S, K142S, K142T, R143P, G144F, G144W, G144Y, E145D, E145S, E145G, K146R, L148A, L148I and the like.