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Enhancement of catalytic activity of enzymes by heating in anhydrous organic solvents: 3D structure of a modified serine proteinase at high resolution

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Title Enhancement of catalytic activity of enzymes by heating in anhydrous organic solvents: 3D structure of a modified serine proteinase at high resolution
 
Creator Sharma, Sujata
Tyagi, Renu
Gupta, M N
Singh, T P
 
Description 34-41
For the first time, it is demonstrated
that exposure of an enzyme to anhydrous organic solvents at optimized high temperature
enhances its catalytic power through local changes at the binding region. Six
enzymes, namely, proteinase K, wheat germ acid phosphatase, α-amylase, β-glucosidase,
chymotrypsin and trypsin were exposed to acetonitrile at 70°C for

three hr. The activities of these enzymes
were found to be considerably enhanced. In order to understand the basis of this
change in the activity of these enzymes, proteinase K was analyzed in detail
using X-ray diffraction method. The overall structure of the enzyme was found
to be similar to the native structure in aqueous environment. The hydrogen
bonding

system of the catalytic triad remained
intact after the treatment. However, the water structure in the substrate
binding site underwent some rearrangement as some of the water molecules were
either displaced or completely absent. The most striking observation concerning
the water structure was the complete deletion of the water molecule which
occupied the

position at the so-called oxyanion hole
in the active site of the native enzyme. Three acetonitrile molecules were
found in the present structure. All the acetonitrile molecules were located in
the recognition site. Interlinked through water molecules, the sites occupied
by acetonitrile molecules were independent of water molecules. The acetonitrile
molecules are involved in extensive interactions with the protein atoms. The
methyl group of one of the acetonitrile molecules (CCN1) interacts simultaneously
with the hydrophobic side chains of Leu 96, Ile 107 and Leu 133. The
development of such a hydrophobic environment at the recognition site
introduced a striking conformation change in lie 107 by rotating its side chain
about Cα-Cβ bond by 180° to bring about the δ-methyl group within the range of
attractive vander Waals interactions with the methyl group of CCN1. A similar
change had earlier been observed in proteinase K when it was complexed to a
substrate analogue, lactoferrin fragment.
 
Date 2013-07-16T05:39:12Z
2013-07-16T05:39:12Z
2001-04
 
Type Article
 
Identifier 0975-0959 (Online); 0301-1208 (Print)
http://hdl.handle.net/123456789/19795
 
Language en_US
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJBB Vol.38(1-2) [February-April 2001]