title: Trypsin inactivation by intact Hymenolepis diminuta (Cestoda): some characteristics of the inactivated enzyme.
abstract: In the presence of intact Hymenolepis diminuta, trypsin was inactivated; intact worms had no apparent effect on subtilisin, pepsin, or papain. Inactivation of trypsin was demonstrable using azoalbumin as a substrate, but the inactivated enzyme retained full catalytic activity against benzoyl-DL-arginine-p-nitroanilide, p-tosyl-L-arginine methyl ester (low molecular weight synthetic trypsin substrates) and p-nitro-p-guanidinobenzoate (an active site titrant). Inactivation was not reversible under conditions of heating, freezing and thawing, or prolonged dialysis of the enzyme. Analyses of inactivated 3H-trypsin by cationic and SDS-polyacrylamide gel electrophoresis, and gel chromatography failed to indicate the presence of a high molecular weight trypsin inhibitor associated with the inactivated enzyme; no low molecular weight, dissociable inhibitor was demonstrable following thermal denaturation of the inactivated enzyme. Analyses of trypsin after incubation in the presence of pulse-labeled worms also failed to demonstrate the presence of any inhibitor of worm origin associated with the inactivated enzyme. The data suggest that inactivation is the result of a small structural or conformational change in the enzyme molecule, a change which partially (rather than totally) inactivates the enzyme towards protein substrates.
mesh_terms: D000418:Albumins / Q000378:metabolism; D000818:Animals; D001586:Benzoylarginine Nitroanilide / Q000378:metabolism; D003956:Dialysis; D005615:Freezing; D006358:Hot Temperature; D006926:Hymenolepis / Q000201:enzymology*; D011480:Protease Inhibitors; D014106:Tosylarginine Methyl Ester / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism; D014361:Trypsin Inhibitors / Q000502:physiology*
chemical_list: D000418:Albumins; D011480:Protease Inhibitors; D014361:Trypsin Inhibitors; C031460:azoalbumin; D014106:Tosylarginine Methyl Ester; D001586:Benzoylarginine Nitroanilide; D014357:Trypsin