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. Author manuscript; available in PMC: 2016 Apr 18.
Published in final edited form as: Chembiochem. 2016 Feb 10;17(5):407–414. doi: 10.1002/cbic.201500613

Figure 4.

Figure 4

A) The rate of PSB decay to the SB is pH-dependent. Glu73, highlighted in the truncated structure, is the only amino acid in the vicinity of the imine with the appropriate pKa for the change in protonation state in the pH regime that alters the rate of the reaction. B) Possible scenario for the less active iminium species at high pH (ionic interaction resulting in a more stabilized iminium species). The protonation of Glu73 reduces the anionic charge stabilization, thus activating the iminium species towards addition of water.