Studies on human high molecular weight (HMW) kininogen. III. Cleavage of HMW kininogen by the action of human salivary kallikrein

Abstract

Human high molecular weight (HMW) kininogen is a single chain with a molecular weight of 120,000 and is cleaved by plasma kallikrein sequentially into a nicked kininogen, an intermediate kinin-free protein (KFP-I), and a stable KFP-II. Here we report a study into the process of cleavage of human HMW kininogen by human salivary kallikrein. On incubation with salivary kallikrein, HMW kininogen was first converted into a nicked kininogen composed of disulfide-linked chains of 62,000 and 56,000 daltons. Subsequently, the nicked kininogen was cleaved into kinin and a KFP, which was apparently of equal size to the nicked kininogen, that is, KFP-I. In contrast to plasma kallikrein, salivary kallikrein did not cleave KFP-I into KFP-II. The two chains were separated by SP-Sephadex C-50 chromatography of reduced and alkylated KFP-I. The N-termini of HMW kininogen and the 62,000-daltons chain were found to be pyroglutamyl-isoleucyl, while that of the 56,000-daltons chain was found to be serine. These results indicate that the sequence of the two chains and kinin in human HMW kininogen is 62,000-daltons chain-kinin-56,000-daltons chain from the N-terminal end of HMW kininogen. Possible processes of cleavage of human HMW kininogen by human plasma and salivary kallikreins are also discussed.