Determination of the rates of formation and hydrolysis of the Schiff bases formed by pyridoxal 5'-phosphate with L-tryptophan and its methyl and <i>n</i>-butyl esters
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Date
2002
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Abstract
The apparent rate constants of the formation (k(1)) and hydrolysis (k(2)) of the Schiff bases formed by pyridoxal 5'-phosphate with L-tryptophan and their methyl and n-butyl esters at a variable pH, 25 degreesC, and an ionic strength of 0.1 M were determined, along with the equilibrium constant (K-pH). The individual rate constants of formation and hydrolysis of the Schiff bases of systems corresponding to different chemical species present in the medium as a function of its acidity were also determined, as were the pK values for the Schiff bases. The influence of the a-carboxyl group on the formation and hydrolysis constants of the Schiff bases, and also on their pK values, is demonstrated.