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Infuence of metal ions on structure and catalytic activity of papain

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Title Infuence of metal ions on structure and catalytic activity of papain
 
Creator Sathish, H A
Kaul, Purnima
Prakash, V
 
Description 18-27
Papain is an endoprotease belonging to cysteine
protease family. The catalytic activity of papain in presence of two different
metal ions namely zinc and cadmium has been investigated. Both the metal ions
are potent inhibitors of the enzyme activity in a concentration dependent
manner. The enzyme loses 50% of its activity at 2x10-4 M of CdCI2 and 4x10-4 M of ZnCI2. It is completely inactivated above 1x10-3
M concentration of either

ZnCI2 or CdCI2. Of the two metal
ions zinc with a ki
value of 5x10-5 M is a
more potent inhibitor than cadmium which has a ki value
of 8x10-5 M.
Both the metal ions have higher
affinity for active site than the substrate. At

concentrations above 1x10-2 M of metal ions the inhibition is not reversible. Calorimetric studies
showed decreased thermal stability of papain upon binding of these metal ions. Far
UV circular dichroic spectral data showed only small changes in the β-structure
content upon binding of these metal ions.
These data are also supported by decrease in the apparent thermal transition
temperature of papain by 5°C upon binding of metal ions indicating
destabilization of the papain molecule. The mechanism of both partial and
complete inactivation of papain in presence of these two metal ions both at
lower and higher concentration has been explained.
 
Date 2012-12-28T11:35:18Z
2012-12-28T11:35:18Z
2000-02
 
Type Article
 
Identifier 0975-0959 (Online); 0301-1208 (Print)
http://hdl.handle.net/123456789/15377
 
Language en_US
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJBB Vol.37(1) [February 2000]