Pentagonal ring waters near the substrate binding site in alanine racemase from S. pneumoniae. The electron density 2Fo-Fc map is contoured at 0.8σ. Residues are shown as sticks, red spheres represent water molecules, and dashed yellow lines represent hydrogen bonds. Residues from the first monomer are colored pink, residues from the second monomer are blue and are denoted with primed numbers. The PLP-bound Lys residue (LLP) is grey. For simplicity, only some of the residues are shown.