Coupling of functional hydrogen bonds in pyridoxal-5'-phosphate-enzyme model systems observed by solid-state NMR spectroscopy

The solid-state NMR spectroscopy technique is employed to study and describe the coupling of functional hydrogen bonds in the models of the confactor pyridoxal-5'-phosphate (PLP) with carboxylic acids that mimic the confactor of various enzyme active sites. The analysis proves a shift in the proton to the Schiff based nitrogen, followed by an increase in the positive charge of the nitrogen atom, which can be avoided by introducing an aromatic substituent in the model.