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Kinetics of inhibition of bovine cathepsin S by bovine stefin B
Author(s) -
Turk Boris,
C̆olić Adrijana,
Stoka Veronika,
Turk Vito
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)80405-2
Subject(s) - kinetics , chemistry , dissociation (chemistry) , hydrolysis , cathepsin , substrate (aquarium) , enzyme kinetics , enzyme , stereochemistry , medicinal chemistry , biochemistry , active site , biology , ecology , physics , quantum mechanics
The kinetics of the complex formation between bovine cathepsin S and bovine stefin B was studied by conventional and stopped‐flow techniques. The inhibition at low inhibitor concentrations was tight and reversible ( k ass = 5.8 × 10 7 M −1 · s −1 , k diss = 4.9 × 10 −4 s −1 at pH 6.0 and 25°C), whereas at higher inhibitor concentrations it was pseudo‐irreversible ( k ass = 6.14 × 10 7 M −1 · s −1 ). The complex was formed directly lacking the fast preequilibrium step with the dissociation equilibrium constant of ~ 8 pM. The competitive nature of inhibition was confirmed. The k ass was found to be pH‐independent between pH 6.0 and 7.5 and decreased at lower or higher pH values in a way that strongly suggests involvement of two ionizable groups in the interaction (p K 1 = 5.2, p K 2 = 8.3). The enzyme‐substrate interaction seems to be influenced by different ionizable groups (p K 1 = 4.4, p K 2 = 7.8).