The pH-Rate Profile for the Hydrolysis of a Peptide Bondстатья из журнала
Аннотация: The rate of hydrolysis of N-(phenylacetyl)glycyl-d-valine (PAGV), an acyclic penicillin G analogue, at pH 0, 1, 3, 5, 7, 9, 11, 13, and 14 has been measured at 37 °C and a pH-rate profile constructed. At each pH, hydrolysis of both the (phenylacetyl)glycyl amide bond and glycyl-d-valine peptide bond was monitored. At pH 3, 5, 7, 9, and 11, the hydrolysis products glycyl-d-valine and d-valine were derivatized with naphthalene-2,3-dialdehyde in the presence of cyanide; the resultant 1-cyano-2-substituted-benz[f]isoindole (CBI) derivatives, which are highly fluorescent, were then quantified using reverse-phase HPLC. The hydrolysis reactions were explicitly shown to be first-order in peptide concentration at pH 5 and 9, and all rates were shown to be independent of the buffer concentration. The rates at pH 0, 1, 13, and 14 were measured in 1 M DCl, 0.1 M DCl, 0.1 M NaOD, and 1 M NaOD, respectively, and the hydrolysis products were detected by 1H NMR. The first-order rate constants obtained from the above reactions were fit to the general equation k = kH20 + kH30+[H3O+] + kOH−[OH-] to yield the following results: for hydrolysis of the (phenylacetyl)glycyl bond, kH2O = (9.05 ± 6.36) × 10-11 s-1, kH3O+ = (1.60 ± 1.04) × 10-6 M-1 s-1, and kOH− = (1.11 ± 0.73) × 10-6 M-1 s-1; and for hydrolysis of the glycyl-d-valine bond, kH2O = (8.23 ± 4.33) × 10-11 s-1, kH3O+ = (1.67 ± 0.80) × 10-6 M-1 s-1, and kOH− = (1.16 ± 0.56) × 10-6 M-1 s-1. At pH 7, the hydrolysis of both the (phenylacetyl)glycyl amide bond and glycyl-d-valine peptide bond is dominated by kH2O. The corresponding half-life for (phenylacetyl)glycyl bond hydrolysis is 243 years (with a range of 143−817 years within experimental error), while that for glycyl-d-valine bond hydrolysis is 267 years (with a range of 175−564 years).
Год издания: 1998
Авторы: Robert M. De Smith, David E. Hansen
Издательство: American Chemical Society
Источник: Journal of the American Chemical Society
Ключевые слова: Analytical Chemistry and Chromatography, Chemical Synthesis and Analysis, Antibiotics Pharmacokinetics and Efficacy
Открытый доступ: closed
Том: 120
Выпуск: 35
Страницы: 8910–8913