Fig. 2
From: Direct visualization of critical hydrogen atoms in a pyridoxal 5′-phosphate enzyme
Internal aldimine reactivity and substrate activation. a Internal aldimine state in the AAT-α-methylaspartate neutron structure. Here and in Figs. 3 and 5, the light blue mesh is the 2|F o|−|F c| nuclear scattering length density at 1σ and the magenta mesh is the omit |F o|−|F c| difference nuclear scattering length density at 3σ. For clarity, the omit |F o|−|F c| difference nuclear scattering maps are presented for deuterium atoms on PLP. The dashed lines indicate hydrogen bonds. b Michaelis complex and proposed substrate activation with the proton transferred upon substrate binding shown in red. A direct or indirect proton transfer mechanism is plausible. Two possible resonance structures of the internal aldimine are shown
