Water catalysis of peptide hydrogen isotope exchange

The temperature dependence of the hydrogen-tritium and deuterium-hydrogen exchange reactions in poly(DL-alanine) has been reexamined. The results indicate a significant contribution to the observed exchange rates from the water-catalyzed reaction at pD values near pDmin. The activation enthalpy for...

Full description

Saved in:
Bibliographic Details
Published in:Biochemistry (Easton) 1983-02, Vol.22 (4), p.910-917
Main Authors: Gregory, Roger B, Crabo, Lars, Percy, Amy J, Rosenberg, Andreas
Format: Article
Language:English
Subjects:
Calorimetry
Chemical Phenomena
Chemistry
Deuterium
hydrogen-deuterium exchange
Hydrogen-Ion Concentration
hydrogen-tritium exchange
Kinetics
Mathematics
Peptides
poly(DL-alanine)
Temperature
Tritium
Water
Citations: Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The temperature dependence of the hydrogen-tritium and deuterium-hydrogen exchange reactions in poly(DL-alanine) has been reexamined. The results indicate a significant contribution to the observed exchange rates from the water-catalyzed reaction at pD values near pDmin. The activation enthalpy for water-catalyzed deuterium-hydrogen exchange in poly(DL-alanine) is found to be 21 kcal mol-1. As a result, the contribution to the observed exchange rate from the water-catalyzed reaction increases with increasing temperature which in turn leads to broad, shallow pD minima and the appearance of apparent reaction orders with respect to [D+] and [OD-] that are substantially less than first order over an extended range of pD values. The importance of water catalysis in protein hydrogen exchange is demonstrated by a reanalysis of data for the exchange of single protons in bovine pancreatic trypsin inhibitor [Hilton, B.D., & Woodward, C. K. (1979) Biochemistry 18, 5834; Richarz, R., Sehr, P., Wagner, G., & Wüthrich, K. (1979) J. Mol. Biol. 130, 19]. The pD dependence of these protons can be explained in terms of an increased contribution from water catalysis.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00273a031