COMPLETE AMINO-ACID-SEQUENCE OF AN ACIDIC, CARDIOTOXIC PHOSPHOLIPASE A(2) FROM THE VENOM OF OPHIOPHAGUS HANNAH (KING COBRA) - A NOVEL COBRAVENOM ENZYME WITH PANCREATIC LOOP

A phospholipase A(2) (OHV A-PLA(2)) from the venom of Ophiophagus hann ah (King cobra) is an acidic protein exhibiting cardiotoxicity, myotox icity, and antiplatelet activity. The complete amino acid sequence of OHV A-PLA(2) has been determined using a combination of Edman degradat ion and mass spectrometric techniques. OHV A-PLA(2) is composed of a s ingle chain of 124 amino acid residues with 14 cysteines and a calcula ted molecular weight of 13719 Pa. It contains the loop of residues (62 -66) found in pancreatic PLA(2)s and hence belongs to class IB enzymes . This pancreatic loop is between two proline residues (Pro 59 and Pro 68) and contains several hydrophilic amino acids (Ser and Asp). This region has high degree of conformational flexibility and is on the sur face of the molecule, and hence it may be a potential protein-protein interaction site. A relatively low sequence homology is found between OHV A-PLA(2) and other known cardiotoxic PLA(2)s, and hence a contiguo us segment could not be identified as a site responsible for the cardi otoxic activity. (C) 1997 Academic Press.