Comparison of human high molecular weight kininogen digestion by plasma kallikrein and by plasmin. A revised method of purification of high molecular weight kininogen.

Both kallikrein and plasmin readily released 112,000 and 102,000 molecular weight derivatives from purified human high molecular weight (HMW)-kininogen. In each instance, these early digestion products were composed of disulfide-linked chains of 64,000 and 58,000 molecular weights. Under the experimental conditions used, kallikrein failed to release additional cleavage fragments from HMW-kininogen when it had been previously digested by plasmin, whereas HMW-kininogen pretreated with kallikrein was then cleaved by plasmin into several derivatives of decreasing molecular size. The profound molecular changes induced by plasmin were only accompanied by partial kinin release. Plasmin cleavage dissociated procoagulant activity from at least one antigenic site of HMW-kininogen light chain. Moreover, kinin activity could be released from a cleavage product of HMW-kininogen containing light but not heavy chain antigens, indicating that plasmin had cleaved this kininogen on the N-terminal side of the bradykinin region of the molecule. Cleavage of HMW-kininogen by kallikrein readily released bradykinin, whereas kinin release by plasmin was slower and the cleavage pattern different. It is, therefore, unlikely that plasmin is a major source of bradykinin release in plasma. A method of isolating HMW-kininogen from human plasma is described that provides a homogeneous single band of kininogen, with a recovery of approximately 44% with respect to that in plasma in a period of 5 days.