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Kinetic and thermodynamic study of the reaction of pyridoxal 5′‐phosphate with L ‐tryptophan
Author(s) -
Echevarría Gerardo R.,
Santos José G.,
Basagoitia Andrea,
Blanco Francisco García
Publication year - 2005
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.893
Subject(s) - chemistry , ionic strength , hydrolysis , reaction rate constant , tryptophan , pyridoxal , pyridoxal 5 phosphate , pyridoxal phosphate , equilibrium constant , phosphate , schiff base , reaction rate , kinetics , medicinal chemistry , organic chemistry , stereochemistry , cofactor , enzyme , catalysis , amino acid , aqueous solution , biochemistry , physics , quantum mechanics
The apparent rate constants for formation ( k 1 ) and hydrolysis ( k 2 ) of the Schiff bases formed by reaction of pyridoxal 5′‐phosphate with L ‐tryptophan were determined at various pH values, at different temperatures and at constant ionic strength (0.1 M ). Also obtained were the elementary rate constants for formation and hydrolysis of the Schiff bases corresponding to the different chemical species present in the media, and the p K values of the Schiff's bases. The activation and thermodynamic parameters for the formation and hydrolysis of the Schiff's bases also were determined. Some of the Δ H 0 and Δ S 0 values for the individual processes were found to be positive. In basic media the enthalpic factor is unfavorable but the entropic contribution leads to a negative Δ G 0 . Copyright © 2004 John Wiley & Sons, Ltd.
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