Isolation and structure of T-kinin.

T-kinin, a previously undescribed peptide containing bradykinin, has been isolated following treatment of rat plasma with trypsin (1 mg/ml). The liberated T-kinin, which contracts the rat uterus, was isolated by procedures including OM-cellulose, Biogel P-4 and reverse-phase high-performance liquid chromatography. The final material had a single N-terminal isoleucine and was shown by amino acid analysis and sequence determination to have the structure of the undecapeptide Ile-Ser-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg (isoleucyl-seryl-bradykinin). The relationships of the protein from which T-kinin is cleaved (T-kininogen) to other known kininogens is discussed.