Direct angiotensin II formation by rat submandibular gland kallikrein

Submandibular gland kallikrein EC 3.4.21.8] of male Sprague-Dawley rats was purified by chromatography on soybean trypsin inhibitor (SBTI)-CH-Sepharose 4B, DEAE-Sephadex A-50, aprotinin-CH-Sepharose 4B and Sephadex G-100 columns and preparative isoelectrofocusing. The molecular weight of the kallikrein was estimated to be 30,000 by Sephadex G-100 gel filtration and 29,000 by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Isoelectric points ranged from pH 3.55 to 4.30. The kinin formed at pH 8 by this kallikrein from bovine low molecular weight (LMW) kininogen showed the same behavior as lysyl-bradykinin on HPLC in a solution of ammonium biphosphate containing acetonitrile. At physiological pH, this kallikrein also generated angiotensin II, a potent vasopressor, from human plasma protein. Rat submandibular gland kallikrein differs from tonin in the isoelectric point, the optimal pH for angiotensin II formation and the type of kinin formed. The tissue kallikrein might play a role in the regulation of local blood flow in view of its ability to form both vasoconstrictive and vasodilatory peptides.