SYNTHESIS OF PEPTIDES BY FRAGMENT CONDENSATION ON A SOLID SUPPORT

Determination of human plasma kininogen by a single radial immunodiffusion method and the bradykinin equivalent

An SRI method is presented for the quantitation of native human plasma kininogen using a monospecific high avidity antiserum prepared against the conformational determinants of kininogen heavy chain (HC antigen). The SRI value of total human plasma kininogen averaged 0.260 +/- 0.052 g/l (+/- 2 SD) using a standard curve of normal human plasma in each assay (measuring range 0.016-0.260 g/l). The SRI data, confirmed by RIA, were compared with determination of the bradykinin equivalent by bioassay 4.30 +/- 0.052 mg/l (+/- 2 SD), generally accepted as a measure of total plasma kininogen. The SRI method does not discriminate between LMr and HMr kininogen but detects an increase of total kininogen independently of bradykinin release as a consequence of activated proteolysis. It is suggested that the SRI method can be applied to study levels of kininogen in clinical research.

Isolation and immunologic properties of a heterogeneous antigen with the characteristics of the heavy chain of human plasma kininogen

Kininogen antigen was purified from human plasma fraction IV by ion exchange chromatography, gel filtration and affinity chromatography with antibody specific immunoadsorbents. The immunologically pure glycoprotein had a mol. wt of approximately 60,000 and only one polypeptide chain by SDS-PAGE. An extensive charge heterogeneity by isoelectric focusing and gel filtration on polyacrylamide agarose could only in part depend on a comparatively high sialic acid content, but may be caused by differences in the carbohydrate structures sustained by lectin-binding heterogeneity on Con A-Sepharose. This antigen shares a dominating determinant with native plasma kininogens shown by complete patterns of identity in immunochemical analyses and with the monospecific antisera developed in rabbits against the heterogeneous components. The similar size, amino acid composition, low histidine content, lack of N-terminal amino acid and antigenic homogeneity fit all the so far known characteristics of the human kininogen heavy chain. Notably the antigenic determinant is resistant to degradation by activated kallikrein. This antigen with unimpaired immunologic activity may be a useful tool for preparation of antiserum for immunochemical determination of human plasma kininogen.

Potentiation of bradykinin with synthetic peptides on guinea pig ileum

Potentiation of the activity of bradykinin on the isolated guinea pig ileum was studied using a designed test system with the synthetic peptides Leu-Val-Glu-Ser-Ser-Lys, Thr-Pro-Val-Ser-Glu-Lys, derivatives of the former coupled to the N- and C-terminals of bradykinin and two peptides with phenylalanine substituted with its isomer L-3-amino-3-phenylpropanoic acid in the 5- and 5,8-positions in bradykinin respectively. On average, two times potentiation effects were obtained at 10-6 to 10-8 M concentrations of the peptides. After elimination of the basic lysine no potentiation occurred with synthetic Leu-Val-Glu-Ser-Ser. With the [beta Phe5,8]-bradykinin a mixed sensitizing/potentiating effect was observed, suggesting that a separation of the two effects may be difficult with an intact receptor structure of this kind. This peptide was not hydrolyzed by carboxypeptidase B or chymotrypsin.