Abstract: A method for synthesizing aromatic amino acids according to one aspect of the present invention includes processes of: (a) of preparing a thermostable a Thermus thermophilus aspartate aminotransferase by culturing an E. coli BL21(DE3) cell transformed with a vector comprising a gene encoding the Thermus thermophilus aspartate aminotransferase; (b) contacting the thermostable Thermus thermophilus aspartate aminotransferase of (a) with an amino donor and an amino acceptor at a temperature range of 50-80° C. to obtain an aromatic amino acid; (c) precipitating the aromatic amino acid of (b); and (d) recovering the thermostable Thermus thermophilus aspartate aminotransferase.

Abstract: A synthesis method of aromatic amino acids according to one aspect of the present invention includes a process of preparing thermostable enzyme, a process of amino-transferring reaction and a process of product precipitation and enzyme recycling. The process of preparing thermostable enzyme comprises an isolation step of the gene of Thermus thermophilus aspartate aminotransferase (TtAspAT), a construction step of the TtAspAT gene in an expression vector, and a transformation step of host cells with the TtAspAT gene-harboring vector for producing a plurality of TtAspAT. The process of amino-transferring reaction catalyzed by TtAspAT, in which an amino group from an amino donor is transferred to the carbonyl group of a keto acid (the amino acceptor) through an amino-transferring reaction at the temperature between 50° C. and 80° C. for a reaction time from 30 to 90 minutes to produce aromatic amino acids.

Abstract: The present invention relates to mutant D-amino acid aminotransferase, including nucleic acids encoding mutant D-amino acid aminotransferase. The mutant D-amino acid aminotransferase of the present invention is obtained by the substitution of the glutamate residue at position 13 of wild type D-amino acid aminotransferase from Bacillus sphaericus with hydrophobic amino acids. The mutant D-amino acid aminotransferase can be used in the production of D-amino acid and the conversion of glutaryl-7-aminocephalosporanic acid from cephalosporin C. The present invention also includes replica-paper staining method for screening the cells expressing high DAT activity.