Hyperconjugation promoted by hydrogen bonding between His98/His241 and a carboxyl group contributes to tyrosine decarboxylase catalysis

Abstract

The utility of the σ → π* hyperconjugation in pyridoxal 5′-phosphate (PLP)-dependent tyrosine decarboxylase (TyDC) is demonstrated here for the first time. His98 and His241 form hydrogen bonds with the carboxyl group of an external aldimine and contribute to the hyperconjugation of TyDC from Lactobacillus brevis. The dihedral angle of C–Cα–N_SB–C4′ in PLP–substrate covalent complexes was found to be vital to the decarboxylation efficiency of TyDC.