Purification and partial characterization of cat colon and submandibular gland kallikreins.

Kallikreins from cat colon and submandibular gland have been purified by acetone fractionation of tissue extracts, DEAE-Sephacel ion-exchange chromatography, rho-aminobenzamidine Sepharose 4B affinity chromatography and gel filtration on Sephadex G-75. They were of similar M.W., approximately 40,000, and each comprised five forms by isoelectric-focusing (pI 4.1-4.8). Both enzymes were potent kininogenases and exhibited similar specificities with synthetic ester and amide substrates. They were susceptible to a range of protease inhibitors. Surprisingly, neither was sensitive to aprotinin yet both were partially inhibited by soya-bean trypsin inhibitor. They were indistinguishable in our immunological tests. An acidic esterase (pI 2.2-3.5) of M.W. 120,000 was isolated from cat stomach by the same procedure. While it exhibited weak immunologic similarity to cat submandibular gland kallikrein, it had negligible kininogenase activity and different substrate and inhibitor specificities to the two kallikreins. It is concluded that similar tissue kallikreins are present in the colon and submandibular gland of the cat but are distinct from this cat stomach esterase.