EFFECT OF PROTEOLYTIC ACTIVITY ON ISOLATION AND STABILITY OF PLATELET PROTEINS

The effect of proteolytic activity in blood platelets on the isolation and stability of platelet albumin and platelet fibrinogen has been investigated. It has been shown that the protease has maximum activity at pH 5 and produces marked structural alteration of the albumin molecule which can be followed spectrophotometrically. Starch gel electrophoresis reveals that the albumin molecule is split into two smaller fragments by the enzyme. Freshly prepared platelet fibrinogen resembles plasma fibrinogen in sedimentation, gel filtration and electrophoretic properties. On storage, however, platelet fibrinogen breaks down to three components, one of which could not be detected in the plasmin digest of plasma fibrinogen. Attempts to isolate platelet albumin and fibrinogen free of associated proteolytic activity by a variety of methods were unsuccessful, suggesting complex formation between the enzyme and its substrate. It has been concluded that the properties of a particular platelet protein can only be determined when an effective method to inhibit the proteolytic activity has been developed. © 1969.