title: Human cathepsin B. Application of the substrate N-benzyloxycarbonyl-L-arginyl-L-arginine 2-naphthylamide to a study of the inhibition by leupeptin.
abstract: 1. The kinetic parameters Kcat. and Km were determined for the hydrolysis of some arginine naphthylamides by human cathepsin B. 2. A new and efficient synthesis of Z-Arg-Arg-NNap (benzyloxycarbonyl-L-arginyl-L-arginine 2-naphthylamide) was developed. 3. Z-Arg-Arg-NNap was a specific and sensitive substrate for cathepsin B, and was used for kinetic studies. 4. Values of kcat. were maximal in the pH range 5.4--6.2, and depended on a single ionizing group of pKa 4.4. 5. Leupeptin was a purely competitive inhibitor of human cathepsin B. 6. The effect of pH on the apparent inhibitor constant, Ki (app.), was determined. Ki (app.) was pH-independent in the range pH 4.3--6.0, with the mean value 7 x 10(-9) M.
mesh_terms: D001120:Arginine / Q000031:analogs & derivatives*; D001587:Benzoylarginine-2-Naphthylamide / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D002403:Cathepsins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D007976:Leupeptins / Q000494:pharmacology*; D009842:Oligopeptides / Q000494:pharmacology*
chemical_list: D007976:Leupeptins; D009842:Oligopeptides; D001587:Benzoylarginine-2-Naphthylamide; C028469:N-benzyloxycarbonylarginyl-L-arginine-2-naphthylamide; D001120:Arginine; D002403:Cathepsins