Purification and partial characterization of the phospholipase A(2) and co-lytic factor from sea anemone (Aiptasia pallida) nematocyst venom

Functional nematocysts of one specific morphological class, the penetrant m icrobasic mastigophores, were isolated from the sea anemone, Aiptasia palli da. These nematocysts contain a multicomponent venom composed of several pr oteins, including those with neurotoxic, hemolytic. and lethal activities. Hemolytic activity is produced by at least three synergistic venom proteins . One of these proteins is identified as a phospholipase A(2) (EC 3.1.1.4) which exists in two isozymic forms, alpha and beta, with molecular weights of 45,000 and 43,000, respectively. The beta isozyme has been purified to h omogeneity. It is a single-chained glycoprotein with an isoelectric point ( pI) of 8.8 and represents 70% of the phospholipase activity of the venom, T he activity of the beta isozyme is relatively labile and is inactivated by 3.5 M urea or by heating at 45 degrees C. It is most stable at pH 4.0 and l oses 50% of its activity at pH values below 3.5 and above 8.0. A second ven om protein has also been purified. It is essential for the hemolytic activi ty of the venom and is termed co-lytic factor (CLF). It is a monomeric glyc oprotein having a pi of 4.5. CLF has a molecular weight of approximately 98 ,000, a sedimentation coefficient of 4.8 S, and is prolate in shape, having a frictional ratio of about 1.6. CLF constitutes about 1.25% of the total venom protein and is assayed by reversing fatty acid inhibition of the veno m hemolysis activity. (C) 1999 Elsevier Science Ltd. All rights reserved.