PMID:15801779

Citation	Lo, HH, Hsu, SK, Lin, WD, Chan, NL and Hsu, WH Asymmetrical synthesis of L-homophenylalanine using engineered Escherichia coli aspartate aminotransferase. Biotechnol. Prog. 21:411-5
Abstract	Site-directed mutagenesis was performed to change the substrate specificity of Escherichia coli aspartate aminotransferase (AAT). A double mutant, R292E/L18H, with a 12.9-fold increase in the specific activity toward L-lysine and 2-oxo-4-phenylbutanoic acid (OPBA) was identified. E. coli cells expressing this mutant enzyme could convert OPBA to L-homophenylalanine (L-HPA) with 97% yield and more than 99.9% ee using L-lysine as amino donor. The transamination product of L-lysine, 2-keto-6-aminocaproate, was cyclized nonenzymatically to form Delta(1)-piperideine 2-carboxylic acid in the reaction mixture. The low solubility of L-HPA and spontaneous cyclization of 2-keto-6-aminocaproate drove the reaction completely toward L-HPA production. This is the first aminotransferase process using L-lysine as inexpensive amino donor for the L-HPA production to be reported.
Links	PubMed Online version:10.1021/bp049756i
Keywords	Aminobutyrates/chemical synthesis; Aspartate Aminotransferases/chemistry; Aspartate Aminotransferases/genetics; Aspartate Aminotransferases/metabolism; Chromatography, High Pressure Liquid; Escherichia coli/enzymology; Mass Spectrometry; Mutagenesis, Site-Directed; Protein Engineering
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