Correlation of Enzymatic Activity and Anticoagulant Properties of Phospholipase A2

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Abstract
Some highly purified phospholipases A from the venom of Viperidae, Crotalidae and Elapidae have anticoagulant properties. All phospholipases which exhibited anticoagulant properties are characterized by a high isoelectric point, but not all strongly basic phospholipases are anticoagulant. Anticoagulant phospholipases hydrolyse highly packed monomolecular films of phospholipids without any lag time, while non-anticoagulant phospholipases present considerable induction times indicative of a low penetrating power. When the ester linkages in the procoagulant lipids were replaced by the non-hydrolysable ether bonds, the mixture retained its clotting ability even in the presence of phospholipases; this suggests that anticoagulant phospholipases prevent clot formation by hydrolysis of phospholipids. This was confirmed by chemical modification of phosholipases, vis, alkylation of the activecentre histidine with 1-bromo-octan-2-one. This modification yielded proteins which had lost their anticoagulant properties, but which retained a high affinity for phospholipids.