Exploring the bifunctionality of aminotransferases in the arogenate route of <scp>l</scp> -tyrosine synthesis

l-Tyrosine (l-Tyr) is not only a proteinogenic amino acid, but is also a high value natural aromatic compound that serves as a precursor for the biosynthesis of valuable biologically active compounds of pharmaceutical and food industries. In organisms that use the arogenate route for l-Tyr synthesis, a prephenate aminotransferase (PAT) is essential. Studies have demonstrated that this activity is not found independently, but is housed by other aminotransferases. The <i>dapC</i> encoding <i>N</i>-succinyldiaminopimelate aminotransferase (S-DAPAT) of <i>Corynebacterium glutamicum</i> has previously been shown to function as a bifunctional PAT-competent enzyme, as it displays both S-DAPAT and PLP-dependent PAT activities, and its deletion leads to l-Tyr bradytrophy. In this context, a comprehensive biochemical, structural, and phylogenetic characterization of DapC_Cg has been carried out to get clues in the acquisition of PAT activity. Similar to many PAT-competent enzymes, the purified enzyme displayed a strong preference for l-glutamate (l-Glu) as the amino donor to a lesser extent, for l-aspartate (l-Asp) as amino group donors. High prephenate concentrations resulted in substrate inhibition of the enzyme. Sequence and structural alignments with enzymes known to possess PAT activity have shown that key residues that may be critical for activity were conserved. Furthermore, phylogenetic analysis, supported by structural and sequence alignments shed light on the evolutionary trajectory of PAT activity. Based on their evolutionary distance and similarity to S-DAPAT of <i>C. glutamicum</i> in the conserved residues for PAT activity, aminotransferases encoded by <i>pat</i> and <i>hisC</i> of <i>C. glutamicum</i> have been suggested to be involved in l-tyrosine biosynthesis in <i>C. glutamicum</i>.HighlightsDapC bifunctionality in <i>C. glutamicum</i> was characterizedKey residues for prephenate aminotransferase activity were proposedEnzymes with potential to exhibit PAT activity in <i>C. glutamicum</i> were proposed.