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  • Title: Regulation of the activity of lysosomal cysteine proteinases by pH-induced inactivation and/or endogenous protein inhibitors, cystatins.
    Author: Turk B, Bieth JG, Björk I, Dolenc I, Turk D, Cimerman N, Kos J, Colic A, Stoka V, Turk V.
    Journal: Biol Chem Hoppe Seyler; 1995 Apr; 376(4):225-30. PubMed ID: 7626231.
    Abstract:
    The kinetics of pH-induced inactivation of human cathepsins B and L was studied by conventional and stopped-flow methods. The inactivation of both enzymes was found to be an irreversible, first-order process. The inactivation rate constants increased exponentially with pH for both enzymes. From log kinac vs pH plots, 3.0 and 1.7 protons were calculated to be desorbed for pH-induced inactivation of cathepsins L and B. Cathepsin B was thus substantially more stable than cathepsin L (approximately 15-fold at pH 7.0 and 37 degrees C). Cathepsin B was efficiently inhibited by cystatin C at pH 7.4, whereas the inhibition by stefin B and high molecular weight kininogen was only moderate. In contrast, cathepsin L was efficiently inhibited by both chicken cystatin and stefin B at this pH kass approximately 3.3 x 10(7) m-1 s-1).
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