A model system for the hydrogen bonded chain in the active centre of the maltodextrinphosphorylase - A FTIR study

Model systems for the hydrogen bonded chain in the active centre of maltodextrinphosphorylase are synthesized and studied by FTIR spectroscopy. A hydrogen bonded system between an amine, the phosphate group of pyridoxalphosphate (PLP) and the phosphate group of glucose-1-phosphoric acid (GLC-1-P) causes an intense continuum in the IR spectrum, indicating that this hydrogen bonded chain shows large proton polarizability owing to collective proton tunnelling in multi-minima proton potentials. If the sodium salt of stearic acid is added to this hydrogen bonded chain, a very intense continuum is again observed. In addition, the carboxylate group of the stearic acid sodium salt becomes partially protonated since a v(C=O) vibration of the carboxyl group arises at 1678 cm(-1). The protons are located in this additional part of the chain.