Kinetic study of the Schiff-base formation between glycine and pyridoxal 5′-phosphate (PLP), pyridoxal (PL), and 5′-deoxypyridoxal (DPL)

Abstract

The formation of Schiff bases between pyridoxal 5′-phosphate (PLP), pyridoxal (PL), 5′-deoxypyridoxal (DPL), and glycine has been investigated as a function of proton concentration at 25 °C and 0.1 mol dm^–3 ionic strength. Ionization constants as well as equilibrium and microscopic kinetic constants of the ionic species present in solution have been determined.

The results show that all the protonatable groups of the aldehyde molecule are involved in the intramolecular acidic catalysis of the dehydration process undergone by the α-hydroxyamine intermediate. Results also reveal that the formation of Schiff base with pyridoxal is greatly affected by the formation of the cyclic hemiacetal of this aldehyde.