Non-identity of reaction centres for pyrophosphatase and toxic actions of cardiotoxin II: The status of cardiotoxin II as a metalloprotein.
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Date
1983-03
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Abstract
Cardiotoxin II of the Indian cobra (Naja naja) contains approximately four Mg2+
per mol. Complete demetallation of the toxin is achieved by three cycles of treatment with
ethylenediamine tetraacetate and gel filtration. Reconstitution of toxin by treatment of the
apo-protein with Mg2+ restores metal content and inorganic pyrophosphatase activity only to
the extent of two atoms/mol and 65%, respectively. Use of Mg (II)-EDTA in the
reconstitution experiment yields restoration of half the original enzyme activity. Mg2+ is
required for the inorganic pyrophosphatase action of the toxin. A definitive statement on the
non-essentiality of Mg2+ for the lethal toxicity of the toxin is not possible at present, although
experimental observations indicate that demetallated toxin is as toxic as the native toxin.
Based on this and the differing sensitivities of the enzyme and toxic activities of the toxin to
heat, it is suggested that the reaction centres in the toxin for the two activities are different and
that the pyrophosphatase activity is not causally connected with the lethal toxicity of the toxin.
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Keywords
Cardiotoxin II, pyrophosphatase, magnesium, metalloprotein, reaction, centres, cobra
Citation
Achyuthan K E, Ramachandran L K. Non-identity of reaction centres for pyrophosphatase and toxic actions of cardiotoxin II: The status of cardiotoxin II as a metalloprotein. Journal of Biosciences. 1983 Mar; 5(1): 1-6.