16. ウシ血漿中でのキニンの遊離機構(第2回プラズマキニン研究会)

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Plasma kinins such as bradykinin, lysylbradykinin and methionyllysylbradykinin exist in plasma as a kininogen, an inactive precursor protein. The authors foumd that two kinds of kininogens, kininogen's I and II, exist in bovine plasme and they were separated each ohter by gel filtration through a column of Sephadex G-150. The most characteristic point of difference is that plasma kallikrein which was isolated from bovine plasma by adsorption on the surface of glass powder releases kinin only from kininogen I, and not from kininogen II. Kininogen I was unstable in the purification procedures but kininogen II was rather stable. Purified kininogen II is a glycoprotein having a single polypeptied chain andspecific tertiary structure constructed by 6 or 7 disulfide linkages, and it is demonstrated that the bradykinin moiety locates at the middle of the kininogen II molecule. After the disulfide linkages of kininogen II was reduced, the kinin release from the modified kininogen was not observed by the action of pancreatic kallikrein. But, trypsin and snake venom bradykinin releasing enzyme released kinin from the modified No. 4 kininogen as well as from native kininogen II. When kininogen II was treated with BrCN, the peptide which was considered to have the following amino acid sequence was obtained. NH-Lys-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg-Ser-Val-Gln-Val-Homoser-OH From this fragment, kinin was released by the action of venom bradykinin releasing enzyme, trypsin, and also pancreatic kallikrein. Thus, the cleavage of the Met-Lys linkage of the kininogen II by the action of pancreatic kallikrein proceeds only in the native kininogen II molecule. These results suggested that the specific conformation in the neibourhood of the N-terminal amino acid of kallidin was necessary for the enzymatic kinin release by pancreatic kallikrein.
1968-04-30

16. ウシ血漿中でのキニンの遊離機構(第2回プラズマキニン研究会)

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