Glycosyl transferase mutant and method for catalytically synthesizing rebaudioside M by using glycosyl transferase mutant

The invention discloses a glycosyl transferase mutant and a method for catalytically synthesizing rebaudioside M by using the glycosyl transferase mutant. The mutant is obtained by performing mutation on the basis of a glycosyl transferase amino acid sequence shown as SEQ ID NO: 1, performing induced expression on a mutant strain to obtain a mutant enzyme, and catalyzing 20g/L RebE to synthesize 12.8 g/L RebM by using the mutant enzyme as a catalyst and the enzymic method. The kinetic parameters of the mutant S195Q on rebaudioside E and rebaudioside D and the Michaelis constant of the mutant are 56.34 +/-2.02 mu M and 214.48 +/-14.54 mu M respectively, and are 1/3 and 2/5 of those of a wild type. The glycosyl transferase mutant is coupled with sucrose synthase to realize efficient catalytic synthesis of rebaudioside M. According to the present invention, the recombinant strain of the glycosyl transferase UGT76G1 or the mutant thereof and the sucrose synthase is constructed so as to achieve the efficient catal