Purification and characterization of a phospholipase A2 isoenzyme isolated from Lachesis muta snake venom.

A new phospholipase A2 (PLA2) isoenzyme was isolated from Lachesis muta crude venom, and was named LM-PLA2-II. This enzyme was purified by gel filtration on a Sephacryl S-200 HR column followed by reverse-phase chromatography on a C2/C18 column. LM-PLA2-II consists of a single polypeptide chain with an apparent molecular mass of 18 kDa and an isoelectric point at pH 5.4. The amino terminal sequence of the enzyme revealed a high degree of homology with other PLA2s from several sources. LM-PLA2-II has a high indirect hemolytic activity and a potent inhibitory effect on platelet aggregation induced by ADP and collagen. It also produces a significant paw edema reaction in rats. The edematous response in rats was abolished by pretreatment with either indomethacin or dexamethasone, suggesting the involvement of cyclo-oxygenase. Pretreatment of LM-PLA2-II with p-bromophenacyl bromide abolished all of these actions, clearly indicating that the biological activities, including the edematogenic effect, are dependent entirely on its enzymatic activity.