ABSTRACT
Phospholipases A2 serve as pivotal enzymes in the defense and predation of living organisms. They occur in mammals, reptiles, insects, and other invertebrates, and may be expected to exist also in other life forms, including plants and prokaryotes. With the exception of the mammalian sources, however, the sampling-of phospholipases A2 has so far been restricted to the poisonous secretions of snakes and to a much lesser extent of bees, scorpions, jellyfish, and one species of lizard. The preponderance of structurally characterized phospholipases A2 to have been isolated from snake venoms reflects a worldwide interest in defining the lethal agents of poisonous snakes that humans frequently encounter: cobras and kraits, with diurnal hunting patterns and, therefore, higher visibility than nocturnal snakes in ranges populated also by humans; seasnakes, pulled in together with fish in nets; vipers, envenomation from which was invariably lethal until a little over a decade ago; and rattlesnakes and cottonmouths, our New World neighbors.
