<p><b>(A)</b> The hydrophobic patch (Pro225-Arg237) in Alr<sub><i>Tt</i></sub> (PDB 4Y2W) is colored in gray, the active site pocket is shown in orange, the substrate and key amino acids mediating the interactions are shown in sticks, the hydrogen bonding interactions are indicated. The hydrophobic patch and active site pocket of the other three bacterial alanine racemases are shown in same view: <b>(B)</b> the PLP-D-Ala complex of Alr<sub><i>Bst</i></sub> (PDB 1L6G). <b>(C)</b> PLP complex of Alr<sub><i>Cd</i></sub> (PDB 4LUS), <b>(D)</b> PLP and DLY complex of DadX<sub><i>pao</i></sub> (PDB 1RCQ).</p
