Figure 1.

The TIM reaction cycle (Kursula et al. 2001). Residue numbering reflects our multiple sequence alignment. Two different oxyanion holes stabilize the intermediate anionic oxygen. Along the reaction pathway, the catalytic Glu alternates between a general base and acid. The evolutionary importance of the catalytic Lys11, His97, and Glu169 is demonstrated as all correspond to phylogenetic motif residues. Asn9 is not predicted as a phylogenetic motif residue, but is immediately adjacent to one. Most of the residues that mediate the pKa value of Glu169 also correspond to phylogenetic motifs.