Characterization and multifunctionality of two amino acid aminotransferases from the hyperthermophile Thermotoga maritima

This is the authors' abstract. We don't add key points for this paper.

The hyperthermophile Thermotoga maritima possesses a unique peptidoglycan containing an unusual d-lysine. Previously, we identified enzymes involved in the production of d-lysine and d-glutamate, respectively, but the biosynthetic pathway of d-alanine remains unclear. Herein, we characterized two amino acid aminotransferases, aspartate aminotransferase (TM1255), and alanine aminotransferase (TM1698). TM1255 has specific aminotransferase activities toward l-aspartate and l-glutamate as amino donors, while TM1698 has broad substrate specificity with high activities toward l-alanine and l-aminobutyrate as amino donors. Intriguingly, these two enzymes possess racemase activities toward several amino acids and aspartate 4-decarboxylase activity. The catalytic efficiency of both enzymes was highest for aminotransferase activity, followed by aspartate 4-decarboxylase activity. Therefore, TM1255 and TM1698 are novel multifunctional enzymes that have three different activities.