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Effect of <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-amino acids on the functional activity and conformational stability of ribonuclease-A

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Title Effect of -amino acids on the functional activity and conformational stability of ribonuclease-A
 
Creator Shahjee, Hanief M
Rishi, Vikas
Ahmad, Faizan
 
Description 368-376
Using cytidine 2':3' cyclic monophosphate
as a substrate, Km and kcat 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°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).ΔHm
(enthalpy change at Tm)  and Δ Cp (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
ac id 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 ΔGDo
with the help of Gibbs-Helmoltz equation (ΔGDo
= ΔHm (1-298.15/Tm) - ΔCp
[(Tm- 298.15) + 298.15 In (298.15/Tm)])using
known values of Tm, ΔHm and ΔCp suggested
that D- and L-amino acids are compatible with protein stability, for ΔGDo
remained unchanged in the presence of amino acids.
 
Date 2013-07-15T09:30:07Z
2013-07-15T09:30:07Z
2002-12
 
Type Article
 
Identifier 0975-0959 (Online); 0301-1208 (Print)
http://hdl.handle.net/123456789/19780
 
Language en_US
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJBB Vol.39(6) [December 2002]