Convenient Genetic Encoding of Phenylalanine Derivatives through Their α-Keto Acid Precursors

The activity and function of proteins can be improved by incorporation of non-canonical amino acids (ncAAs). To avoid the tedious synthesis of a large number of chiral phenylalanine derivatives, we synthesized the corresponding phenylpyruvic acid precursors.Escherichia colistrain DH10B and strain C321.ΔA.expΔPBAD were selected as hosts for phenylpyruvic acid bioconversion and genetic code expansion using theMmPylRS/pyltRNACUAsystem. The concentrations of keto acids, PLP and amino donors were optimized in the process. Eight keto acids that can be biotransformed and their coupled genetic code expansions were identified. Finally, the genetic encoded ncAAs were tested for incorporation into fluorescent proteins with keto acids.Keywords:keto acids;biotransform;evolution