A stereo representation of the active sites of the holoenzyme structures of C. violaceum Am:PyAT (green) and P. aeruginosa β-A:PyAT (grey) shown superimposed. The cofactor molecules and side chains of the residues within 4.5 Å of the cofactor are shown as stick models. The active-site Lys288 forms a Schiff base with the cofactor PLP in C. violaceum Am:PyAT. In P. aeruginosa β-A:PyAT the cofactor is modelled as free PLP. Cofactor molecules and neighbouring residues are shown as stick models.