Kinetic Studies on the Interactions between Native, Acetylated and Succinylated Trypsin and Natural Proteinase Inhibitors
It is now well established that the amino acid residues, which participate in the active site of trypsin, are located in the contact area between the enzyme and its natural proteinase inhibitors. This has been shown by several lines of experimental evidence: a) the inhibition of trypsin is competitive ; b) trypsin in which the active site Ser 183 is modified with diisopropylfluorophosphate (DFP) does not bind any longer the inhibitors [1, 2]; c) trypsin in which the active site His 46 is modified either by photooxidation [2, 3] or by tosyllysylchloro-methylketone (TLCK) , or by bromoacetone  does not bind some of the inhibitors; d) the pH dependence of the association rate constant between trypsin and the pancreatic [5, 6] or soybean Kunitz , or Kazal inhibitors  indicates that His 46 is involved in the association process; e) finally, the recent reports on the threedimensional structure of the trypsin-pancreatic Kunitz inhibitor complex  and the trypsin-soybean Kunitz inhibitor complex  confirm the kinetic and chemical studies.
KeywordsHydrolysis Titration Carboxyl Fractionation CaCl
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