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<span style="font-size:14.0pt;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";mso-ansi-language:EN-US;mso-fareast-language: EN-US;mso-bidi-language:AR-SA">UDP-galactose 4-epimerase from <i>Escherichia coli: </i>Equilibrium unfolding studies</span>

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Title UDP-galactose 4-epimerase from Escherichia coli: Equilibrium unfolding studies
 
Creator Nayar, Suprabha
Bhattacharyya, Debasish
 
Description 353-360
UDP-galactose 4-epimerase from Escherichia coli is
a homodimer of 39 kDa subunit with non-covalently bound NAD acting as cofactor.
The enzyme can be reversibly reactivated after denaturation and dissociation using
8 M urea at pH 7.0. There is
a strong affinity between the cofactor and the refolded molecule as no
extraneous NAD is required for its reactivation. Results from equilibrium
denaturation using parameters like catalytic activity, circular-dichroism, fluorescence
emission (both intrinsic and with extraneous f1uorophore I-aniline
8-naphthalene sulphonic acid ), 'reductive inhibition' (associated with
orientation of NAD on the native enzyme surface),elution profile from
size-exclusion HPLC and light scattering

have been compiled here. These show that inactivation,
integrity of secondary, tertiary and quaternary structures have different transition
mid-points suggestive of non-cooperative transition. The unfolding process may
be broadly resolved into three parts: an active dimeric holoenzyme with 50% of
its original secondary structure at 2.5 M urea; an active monomeric

holoenzymc at 3 M urea with only 40% of
secondary structure and finally further denaturation by 6 M urea leads
to an inactive equilibrium unfolded state with only 20% of residual secondary
structure. Thermodynamical parameters associated with some transitions have
been quantitated. The results have been discussed with the X-ray
crystallographic structure of the enzyme.
 
Date 2012-12-25T18:47:23Z
2012-12-25T18:47:23Z
2001-12
 
Type Article
 
Identifier 0975-0959 (Online); 0301-1208 (Print)
http://hdl.handle.net/123456789/15321
 
Language en_US
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJBB Vol.38(6) [December 2001]