Characterization of a (R)-selective amine transaminase from Fusarium oxysporum

Amine transaminases are prominent biocatalysts in the production of chiral amines which are indispensable building blocks in asymmetric synthesis. In this study, a new (R)-enantioselective amine transaminase from Fusarium oxysporum (ATFo) was identified by genome mining. ATFo possibly evolved from a branched chain amino acid aminotransferase (BCAT) with key amino acids being changed, which belong to one of the three groups of pyridoxal 5'-phosphate dependent enzymes class IV (PLPDE_IV). The gene of the amine transaminase was functionally expressed and the protein was then purified with a molecular mass of approximately 36 kDa. The purified ATFo demonstrated high stereoselectivity towards (R)-enantiomer of alpha-phenethylamine and other analogues, which clearly indicated its (R) -selectivity. The optimal temperattre and pH for the activities of ATFo were 25 degrees C and 7.0, respectively. Addition of Mn2+ and Zn2+ could greatly enhance the enzyme activity. In addition, the specific activities and stereoselectivities of these ATFo toward various amino donors and amino acceptors were determined. Compared to (5)-selective amine transaminase, the (R)-selective counterpart has been less studied. Given their pivotal role in asymmetric biocatalysis, it is of great importance to find more (R) selective amine transaminases with ability or potential for synthesis of the target compounds. Thus, the discovery of the (R)-selective amine transaminase ATFo is a valuable contribution to the currently small toolbox of these enzymes.