Schiff’s Bases Formed between Pyridoxal 5-Phosphate and 4-Aminobutanoic Acid. Kinetic and Thermodynamic Study

The overall and individual kinetic constants of formation (k1 and k1i) and hydrolysis (k2, kOH and k2i) of the Schiff’s bases formed between pyridoxal 5ʹ-phosphate (PLP) and 4-aminobutanoic acid (GABA) at 10, 20, 25, 30, and 37 °C, a variable pH and a constant ionic strength of 0.1 M (1 M = 1 mol dm^-3) were determined. The formation of a Schiff’s base is an intramolecular acid-catalyzed process. The activation and thermodynamic parameters for the formation and hydrolysis of the Schiff’s bases were also determined. (delta)H and (delta)S for the individual processes were all found to be negative.