POLYBITOXINS - A GROUP OF PHOSPHOLIPASES A(2) FROM THE VENOM OF THE NEOTROPICAL SOCIAL WASP PAULISTINHA (POLYBIA-PAULISTA)

The neotropical wasp Polybia paulista is very aggressive and endemic i n south-east Brazil, where it frequently causes stinging accidents. By using gel filtration on Sephadex G-200, followed by ion-exchange chro matography on DEAE-Cellulose under a pH gradient, a group of four toxi ns (designated as polybitoxins-I, II, III and IV) presenting phospholi pase A(2) (PLA(2)) activities was purified. These toxins are dimeric w ith mel. wts ranging from 115,000 to 132,000 and formed by different s ubunits. The four toxins contain very high sugar contents attached to their molecules (22-43% w/w) and presented different values of pH opti mum from 7.8 to 9.0; when dissociated, only residual catalytic activit ies were maintained. The catalytic activities of polybitoxins (from 18 to 771 mu moles/mg per minute) are lower than that of PLA(2) from Api s mellifera venom and hornetin from Vespa basalis. The polybitoxins pr esented a non-linear steady-state kinetic behavior for the hydrolysis of phosphatidylcholine at pH 7.9, compatible with the negative co-oper ativity phenomena. All of the polybitoxins were very potent direct hem olysins, especially the polybitoxins-III and IV, which are as potent a s the lethal toxin from V. basalis and hornetin from Vespa flavitarsus , respectively; polybitoxin-IV presented hemolytic action 20 times hig her than that of PLA(2) from A. mellifera, 17 times higher than that o f neutral PLA(2) from Naja nigricolis and about 37 times higher than t hat of cardiotoxin from Naja naja atra venom. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.