Two groups of thermophilic amino acid aminotransferases exhibiting broad substrate specificities for the synthesis of phenylglycine derivatives

Thirty two thermophilic amino acid aminotransferases (AATs) were expressed in Escherichia coli as soluble and active proteins. Based on their primary structures, the 32 AATs were divided into four phylogenetic groups (classes I, II, IV, and V). The substrate specificities of these AATs were examined, and 12 AATs were found capable of synthesizing ring-substituted phenylglycine derivatives such as hydroxyl-, methoxy-, and fluorophenylglycines. Eleven out of the 12 AATs were enzymes belonging to two phylogenetic groups namely, one subgroup of the class I family and the class IV family. AATs in these two groups may thus be useful for the synthesis of a variety of ring-substituted phenylglycine derivatives.