Mechanism of kinin release from human low-molecular-mass-kininogen by the synergistic action of human plasma kallikrein and leukocyte elastase.

We have investigated the kinin release from human L-kininogen, a poor substrate for plasma kallikrein, by the synergistic action of human PMN elastase and plasma kallikrein. Although PMN elastase alone failed to generate kinin activity from L-kininogen, combination of PMN elastase with plasma kallikrein was found to be effective for the generation of kinin activity from L-kininogen. Two kinds of kinin, bradykinin and Met-Lys-bradykinin, were found to be released from L-kininogen by the synergistic action of PMN elastase and plasma kallikrein. Pretreatment of L-kininogen with PMN elastase facilitated the kinin release by plasma kallikrein, whereas pretreatment of L-kininogen with plasma kallikrein did not allow kinin release by the action of PMN elastase. These results suggested that PMN elastase would act firstly on L-kininogen to form a kinin containing fragment, from which kinin is released by the action of plasma kallikrein. The kinin-containing fragment was isolated by gel filtration and high-performance liquid chromatography of the elastase digest of L-kininogen. The amino-acid analysis and N-terminal amino-acid sequence analysis revealed that the kinin-containing fragment consisted of 26 amino-acid residues and is formed by cleavage of an Ile-Ser and a Ser-His bond of L-kininogen.