The isolation of a component of the venom of Trimeresurus okinavensis that causes the aggregation of blood platelets.

1. A substance has been isolated from the venom of the Okinawan pit viper (Trimeresurus okinavensis) that causes the aggregation of human blood platelets. The reaction resembles that between platelets and thrombin or connective tissue, in that the platelets release ADP. 2. The purified venom fraction is a protein-polysaccharide, and after Pronase digestion had mol.wt. 4x10(6), containing 10% peptide, 85% neutral sugars and 5% hexosamines. It is distinct from the proteolytic, esterolytic and coagulant materials also present in the venom, and has not been shown to possess any enzymic activity. How it reacts with platelets is not yet known.