Aminotransferase, mutant and application to Sitagliptin preparation

The invention discloses aminotransferase, a mutant and application to Sitagliptin preparation. According to the application, wet thalli obtained by performing fermentation culture on recombinant escherichia coli containing aminotransferase encoding genes are used as biocatalysts; Sitagliptin precursor ketone is used as a substrate; dimethyl sulfoxide is used as a latent solvent; phosphopyridoxal is used as a coenzyme; isopropylamine is used as an auxiliary substrate; a trolamine buffer solution with the pH being 8 to 9 is used as a reaction medium; a reaction system is formed; the biocatalytic reaction is performed under the conditions of the temperature being 30 to 45 DEG C and the stirring speed being 100 to 250 r/min; after the reaction is completed, the reaction liquid is separated and purified; the Sitagliptin is obtained. The aminotransferase and the mutant are used as biocatalysts; the latent carbonyl compound of Sitagliptin precursor ketone is directly used as the substrate; meanwhile, biocatalytic reaction is performed by using isopropylamine as the auxiliary substrate and using the pyridoxal phosphate as the coenzyme; the separation and purification is performed; Sitagliptin with high optical purity is prepared. The method has the advantages that the total yield is 76 percent; the product e.e. value reaches 99 percent.