title: Activation of a latent kinin-generating proteinase in the porcine anterior pituitary.
abstract: This study was conducted to determine whether a kinin-generating proteinase (kininogenase) previously described in the porcine anterior pituitary exists in a latent form. Porcine anterior pituitaries were homogenized in 0.25 M sucrose (pH 7.5) and sequentially centrifuged at 1000 X g for 5 min, 1500 X g for 20 min, 10 000 X g for 20 min, and 105 000 X g for 60 min. The various fractions were assayed for their ability to generate kinins from kininogen and cleave H-D-Pro-Phe-Arg-p-nitroanilide (S-2302) before or after various activation procedures. Untreated pituitary fractions had a small amount of proteolytic activity. However, large increases in kininogenase and S-2302 hydrolytic activity were observed in the 105 000 X g pellet after dialysis, or incubation with trypsin. Repeated freezing and thawing, detergents, phospholipase A2, melittin, plasmin, thrombin, urokinase and Factor Xa failed to activate kininogenase activity in the 105 000 X g pellet. However, plasmin produced massive increases in S-2302 hydrolytic activity. The kininogenase and S-2302 hydrolytic activity was sensitive to inhibition by soybean trypsin inhibitor and aprotinin, and had a broad pH optimum between 7 and 9. The data indicate that the porcine anterior pituitary kininogenase largely exists in a latent form. Also, the porcine anterior pituitary appears to contain an additional latent proteinase which can hydrolyze S-2302.
mesh_terms: D000818:Animals; D004789:Enzyme Activation; D007610:Kallikreins / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D010447:Peptide Hydrolases / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000201:enzymology*; D013347:Subcellular Fractions / Q000201:enzymology; D013552:Swine
chemical_list: D010447:Peptide Hydrolases; D007610:Kallikreins