Abstract: L-Phenylalanine derivatives are key components or intermediates of many anti-tumor compounds. L-4-Methylsulfonyl-phenylalanine may inhibit tumor cell proliferation. At present, L-phenylalanine derivatives are normally produced by chemical resolution or enzymatic method. In this work, the chiral compound L-4-methylsulphonyl-phenylalanine was prepared by enzymatic method from 4-methylsulphonyl-phenylpyruvate and L-aspartic acid. The influence of various factors on the biocatalysis was studied. The optimal temperature and pH value were 37 ℃ and 8. The optimal mass fraction of 4-methylsulphonyl-phenylpyruvate and tween 80 were 8% and 0.6%. 1×10-4 mol/L of Mg2+ can improve the activity of aspartate aminotransferase. Under the optimal conditions, bioconversion rate of 4-methylsulphonyl-phenylpyruvate reached 95% after 12 h. The study provides a new idea for preparing L-phenylalanine derivatives.

Key words: Genetic engineering, Aspartate aminotransferase, Enzymatic synthesis, Amino acid derivative