Enhanced transaminase activity of a bifunctional l-aspartate 4-decarboxylase

摘要: L-Aspartate 4-decarboxylase (Asd) catalyzes mainly the beta-decarboxylation of aspartate and also transamination with alpha-keto acids. To investigate residues that are critical in directing reaction pathway, seven point mutations were designed based on differences between Asd amiontransferases conservative amino acid residues. All mutant Asds purified characterized. The F204W enhanced aminotransferase activity, its ratio to beta-decarboxylase activity was 3.8-fold. Its K(m) values for alpha-ketoglutarate 1.3 0.17 mM, respectively, representing a large increase binding affinity substrates. K347R mutation did not transaminase activity. D360P decreased more specific catalyzing reaction. This is first study successfully increased via site-directed mutagenesis. modeled protein structure reveals how residue may involve specificity, providing insights into comprehending molecular evolution this bifunctional enzyme.