Document Detail


Effect of D-amino acids on the functional activity and conformational stability of ribonuclease-A.
MedLine Citation:
PMID:  22905393     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
Using cytidine 2':3' cyclic monophosphate as a substrate, Km and k(cat) of ribonuclease-A in the presence of different concentrations of D-amino acids (Ala, Ser, Pro and Lys) and their L-isomers were measured at pH 6.0 and 25 degrees C. These kinetic parameters remained unchanged in the presence and absence of D-and L-amino acids. This is the first experimental evidence showing that D-amino acids are compatible with the enzyme function. Values of Tm (midpoint of denaturation), deltaHm (enthalpy change at Tm) and deltaCp (constant-pressure heat capacity change) were also determined from the heat-induced denaturation curves of the protein, measured in the presence and absence of D- and L-isomers of an amino acid at four different pH values. It is shown for the first time that these thermodynamic parameters, within experimental errors, do not depend on the stereospecificity of an amino acid. Estimates of deltaGDo with the help of Gibbs-Helmoltz equation (deltaGDo = deltaHm (1-298.15/Tm)--deltaCp [(Tm-298.15) + 298.15 In (298.15/Tm)]) using known values of Tm, deltaHm and deltaCp suggested that D- and L-amino acids are compatible with protein stability, for deltaGDo remained unchanged in the presence of amino acids.
Authors:
Hanief M Shahjee; Vikas Rishi; Faizan Ahmad
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Indian journal of biochemistry & biophysics     Volume:  39     ISSN:  0301-1208     ISO Abbreviation:  Indian J. Biochem. Biophys.     Publication Date:  2002 Dec 
Date Detail:
Created Date:  2012-08-21     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0310774     Medline TA:  Indian J Biochem Biophys     Country:  India    
Other Details:
Languages:  eng     Pagination:  368-76     Citation Subset:  IM    
Affiliation:
Department of Biosciences, Jamia Millia Islamia, Jamia Nagar, New Delhi 110 025, India.
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