Three Different Classes of Aminotransferases Evolved Prephenate Aminotransferase Functionality in Arogenate-competent Microorganisms

Background: The genes encoding prephenate aminotransferase in arogenate-competent microorganisms for tyrosine synthesis are still unknown. Results: Three different classes of aminotransferase use prephenate as an amino acceptor. Conclusion: Prephenate aminotransferase functionality has arisen more than once during evolution. Significance: This first identification of prephenate aminotransferases in arogenate competent microorganisms affords a better understanding of the origin and fixation of the arogenate route during evolution. The aromatic amino acids phenylalanine and tyrosine represent essential sources of high value natural aromatic compounds for human health and industry. Depending on the organism, alternative routes exist for their synthesis. Phenylalanine and tyrosine are synthesized either via phenylpyruvate/4-hydroxyphenylpyruvate or via arogenate. In arogenate-competent microorganisms, an aminotransferase is required for the transamination of prephenate into arogenate, but the identity of the genes is still unknown. We present here the first identification of prephenate aminotransferases (PATs) in seven arogenate-competent microorganisms and the discovery that PAT activity is provided by three different classes of aminotransferase, which belong to two different fold types of pyridoxal phosphate enzymes: an aspartate aminotransferase subgroup 1 in tested - and -proteobacteria, a branched-chain aminotransferase in tested cyanobacteria, and an N-succinyldiaminopimelate aminotransferase in tested actinobacteria and in the -proteobacterium Nitrosomonas europaea. Recombinant PAT enzymes exhibit high activity toward prephenate, indicating that the corresponding genes encode bona fide PAT. PAT functionality was acquired without other modification of substrate specificity and is not a general catalytic property of the three classes of aminotransferases.