Masanobu Komiya

Primary structure of bovine high molecular weight kininogen: Chemical compositions of kinin-free kininogen and peptide fragments released by plasma kallikrein

High molecular weight (HMW) kininogen found in mammalian blood plasma is one of the functional glycoproteins, which participates in the kallikreinkinin system [l] . Quite recently, a new function of this protein has been suggested by findings of Flaujeac and Williams traits with a deficiency of the kininogen [2,3] . The deficient plasma does not release kinin upon incubation of kallikrein and also has a prolonged activated partial thromboplastin time and inability to form plasmin. These suggest a participation of the kininogen on the intrinsic blood coagulation and fibrinolysis, in addition to the kinin-forming system. In order to realize these physiological functions, it seems important to study the chemical structure of kininogen. Previously, we reported that a few of peptide fragments, in addition to kinin, were liberated from HMW kininogen on the digestion with plasma kallikrein [4]. One of the fragments was found to contain an abnormally high level of histidine (named tentatively histidine-rich peptide), and its amino acid sequence was established [5] . This communication describes further studies on the chemical compositions of kinin-free kininogen and peptide fragments produced from HMW kininogen by plasma kallikrein.

Bovine plasma HMW and LMW kininogens: isolation and characterization of the polypeptide fragments produced by plasma and tissue kallikreins.

There exist at least two types of kininogens with different molecular weight in mammalian blood plasmas, which are named high molecular weight (HMW) and low molecular weight (LMW) kininogens (1). Although their functions in kallikrein-kinin system remain to be investigated, it has been speculated that HMW kininogen participates in the intrinsic kinin releasing system and Imw kininogen in the extrinsic kinin-releasing system. Quite recently, a new function of kininogen has been suggested by findings of Flaujeac (2), Williams (3), and Fitzgerald (4) traits with a deficiency of kininogen. These plasmas do not release kinin appreciably upon incubation of plasma kallikrein and also has a prolonged activated partial thromboplastin time and inability to form plasmin. These facts suggest the participation of the kininogen in the intrinsic blood coagulation and fibrinolysis, in addition to the kinin-forming system.

Homology between bovine high molecular weight and low molecular weight kininogens

Abstract Two bovine kininogens, one with high molecular weight (HMW) and another with low molecular weight (LMW), were compared by peptide mapping, after trypsin digestion, and by polyacrylamide gel electrophoresis, after cleavage with cyanogen bromide. Almost all the fragments derived from LMW kininogen were also found in the peptide map and electropherogram of HMW kininogen. The amino acid sequence of the kallidin-containing peptide obtained from HMW kininogen was identical with that of the peptide from LMW kininogen. These results indicate a high degree of homology between the amino acid sequences of HMW and LMW kininogens.

Protein Components which Relate to the Kinin Releasing System in Bovine Plasma

Blood plasma contains several discrete systems consisting of the sequential conversion of proenzymes into active enzymes, in which their activations lead to a hypotension due to the liberation of vasoactive polypeptide termed kinin, and to thrombosis and hemorrhage due to the formation and lysis of fibrin clot. From physiological point of view, it is of interest how is the kallikrein-kinin system to be concerted with the other enzyme systems, such as blood coagulation and fibrinolysis. Recently, it was suggested that Hageman factor, which is known to have triggering action for the intrinsic coagulation and fibrinolysis systems, also pull the trigger for the activation of kallikreinkinin system. To clarify the above relations, it is extremely important to isolate the pure components, which concern to the liberation of kinin, and to elucidate their interrelations, reconstructing the kinin liberating systems in vitro.

Some Properties of Bovine High Molecular Weight Kininogen

The presence of two kininogens has been shown in human, dog, guinea pig, rabbit and rat plasma by Jacobsen (1–3), in horse plasma by Henriques et al.(4), and in bovine plasma by Yano et al. (5). Pierce and Webster (6) isolated two low molecular weight (LMW) human kininogens with the same molecular weight of about 50,000 but with their kinin sequences carboxyl-terminal in one case and internal in the other. After that, two kininogens of different molecular weight were isolated from human plasma by Jacobsen and Kritz (7). LMW bovine kininogen (kininogen-II) has been highly purified by the groups of Habermann (8) and of Suzuki (9), and it was found by us that the kinin segment, which was thought to lie in the central part of LMW kininogen molecule, was released by trypsin, snake venom kininogenase or hog pancreatic kallikrein but not by glass-or casein-activated bovine plasma kallikrein. High molecular weight (HMW) kininogen (kininogen-I), a sensitive substrate of bovine plasma kallikrein, was isolated from bovine plasma by Yano et al.(10), and it was found that there is a methionyl-lysyl-bradykinin sequence located both at the carboxyl terminus and inside of the polypeptide chain of bovine HMW kininogen (11).