title: Isolation of a thiol-activated T-kininogenase from the rat submandibular gland.
abstract: T-kininogenase (T-kgnase) activity has been investigated in tissues of the rat and submandibular glands of the rat, mouse and guinea pig. Both rat and mouse submandibular homogenates showed high T-kgnase activity. The enzyme has been purified 360-fold from rat submandibular gland homogenate supernatant fluid. The enzyme has an apparent molecular mass of 28 kDa and a pH optimum of 8.0 toward T-kininogen. It cleaved T-kininogen in catalytic quantities to release T-kinin (Ile-Ser-bradykinin) and small quantities of bradykinin and an unknown kinin. The activity of the enzyme was increased 10-fold in the presence of thiol groups (dithiothreitol) and inhibited by leupeptin (90%) and to a lesser extent by aprotinin (49%), TLCK (46%) and soybean trypsin inhibitor (27%). Pepstatin and PMSF did not inhibit the enzyme. Studies on substrate specificity, pH optimum and agents which inhibit T-kgnase activity demonstrate that this enzyme is different from plasma and tissue kallikreins, cathepsin D, esterase A and esterase B (other known kininogenases). It is the first thiol-activated kininogenase to be reported.
mesh_terms: D000818:Animals; D001920:Bradykinin / Q000031:analogs & derivatives / Q000378:metabolism; D002845:Chromatography; D004789:Enzyme Activation / Q000187:drug effects; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007610:Kallikreins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008970:Molecular Weight; D051381:Rats; D011919:Rats, Inbred Strains; D013363:Submandibular Gland / Q000201:enzymology*; D013438:Sulfhydryl Compounds / Q000494:pharmacology*
chemical_list: D013438:Sulfhydryl Compounds; C039065:T-kinin; D007610:Kallikreins; D001920:Bradykinin