Journal of Lipid Research, Vol. 7, 258-263, March 1966
Copyright © 1966 by Lipid Research, Inc.
Lipid monolayers: action of phospholipase A of Crotalus atrox and Naja naja venoms on phosphatidyl choline and phosphatidal choline
Giuseppe Colacicco and Maurice M. Rapport
Department of Biochemistry, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York
The activity of phospholipase A on phosphatidyl choline and phosphatidal choline spread as monolayers on phosphate buffers containing snake venom (Crotalus atrox or Naja naja) was studied by measuring the fall of surface potential as a function of time, pH, film pressure, temperature, and concentrations of phosphate and venom.
At 25°C, pH 7.0, and 0.2 µg of venom per ml, optimal activity was observed with both venoms on both substrates at 12 dynes/cm film pressure on 0.04 m phosphate. Under these conditions, the pH optimum for C. atrox was broad (6.6-7.4) and that for N. naja was sharp (8.0) for the action on phosphatidyl choline, whereas both venoms had a sharp optimum at pH 8.0 in their action on phosphatidal choline. The optimal temperature with phosphatidyl choline was 27.5°C for N. naja and 40°C for C. atrox.
In line with studies of phospholipase A activity in bulk phase in ether, phosphatidal choline was attacked much more slowly than phosphatidyl choline by C. atrox. Under conditions where both venoms had equal activity on phosphatidyl choline, C. atrox was only half as active as N. naja on phosphatidal choline. The studies suggest that the linkage of the hydrophobic chains in glycerophosphatides may affect their interaction with proteins.
Supplementary key words monolayers • snake venoms • phospholipase A • phosphatidyl choline • phosphatidal choline • surface potential • substrate structure • enzyme activity
Submitted on August 31, 1965
Accepted on November 29, 1965
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