Purification and characterization of two kinds of low molecular weight kininogens from rat (non-inflamed) plasma. One resistant and the second sensitive to rat glandular kallikreins.

Two kinds of low molecular weight kininogens (identified as A and B) were isolated from pooled plasma of Sprague-Dawley rats. They show a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence and absence of 2-mercaptoethanol, and the molecular weights are 68,000 for low Mr kininogen A and 73,000 for low Mr kininogen B. Although the molecular weights and amino acid compositions of the low Mr kininogens are similar, rat submaxillary and urinary kallikreins released bradykinin from low Mr kininogen B, whereas low Mr kininogen A was resistant to these enzymes. The COOH-terminal portion of low Mr kininogen A was isolated after cyanogen bromide treatment, and the amino acid sequence of the COOH-terminal 55 residues including the T-kinin (Ile-Ser-bradykinin) was determined. The COOH-terminal portion consists of two sequences with substitution of 4 residues. One peptide corresponds to alpha 1-major acute phase protein (Cole, T., Inglis, A. S., Roxburgh, C. M., Howlett, G. J., and Schreiber, G. (1985) FEBS Lett. 182, 57-61) and the other to the TI-kininogen predicted from a cDNA study (Furuto-Kato, S., Matsumoto, A., Kitamura, N., and Nakanishi, S. (1985) J. Biol. Chem. 260, 12054-12059). The results demonstrate that there exist at least two kinds of low Mr kininogens with clearly different function in rat plasma: one of them, low Mr kininogen A, is a precursor of T-kinin and is resistant to kallikreins, and the second, low Mr kininogen B, is sensitive to tissue kallikreins and shares properties with bovine and human low Mr kininogens. The results also demonstrate that T-kininogen is a mixture of two isoproteins which correspond to alpha 1-major acute phase protein or TI-kininogen, respectively. We could not detect the low Mr kininogen corresponding to the TII-kininogen predicted from the cDNA study of Furuto-Kato et al.