Functionally Important Residues for the Anticoagulant Activity of A Basic Phospholipase A2 from the Agkistrodon Halys Pallas

To identify the anticoagulant region of the phospholipase A2 (PLA2) from the Agkistrodon halys Pallas (class II), four mutants E53G, W70M, T56K, and D67K were produced according to the prediction from the crystal structure and the sequence comparison of the strong, weak and non-anticoagulant PLA2s. A test of blood clotting revealed that E53G and W70M had lost their effects on the blood clotting, while T56K and D67K had enhanced activity. The four residues are located on the same face in the tertiary structure of this enzyme. The result supported the prediction that there exists an anticoagulant region that is composed of some residues that are close to each other in tertiary structure to form a functional face.