Temperature dependence of binding and catalysis for human serum arylesterase/paraoxonase. - Individual Prediction and Prevention of Risks of Immunosuppressive Therapies in Transplantation Access content directly
Journal Articles Biochimie Year : 2014

Temperature dependence of binding and catalysis for human serum arylesterase/paraoxonase.

Abstract

: The influence of temperature upon the hydrolysis of phenyl acetate, catalysed by purified human serum arylesterase/paraoxonase (E. C. 3.1.8.1), was studied in the temperature range 10 °C-40 °C by spectrophotometry in TRIS buffer, pH 8.0, using both initial rate analysis and progress curve analysis. The kinetic parameters (catalytic constant kcat; Michaelis constant Km; product inhibition constant Kp) were determined by nonlinear regression. All parameters increased with temperature, but the ratios kcat/Km and Kp/Km remained practically constant. Binding of both substrate and reaction product (phenol) was exothermic. A negative entropic term accounted for about 50% of the enthalpy change for both the binding and catalytic steps. Thermodynamic analysis suggested that: (1) the rate-limiting step is the nucleophilic attack of the carbonyl group of the substrate by a water molecule, (2) the active site is preorganized with no induced fit, (3) the enzyme-bound calcium plays an important role in stabilizing both the substrate and the transition state. The practical implications of these results are discussed.
Fichier principal
Vignette du fichier
Debord_2014.pdf (637.56 Ko) Télécharger le fichier
Origin : Files produced by the author(s)
Loading...

Dates and versions

hal-00875973 , version 1 (06-06-2014)

Identifiers

Cite

Jean Debord, Jean-Claude Bollinger, Michel Harel, Thierry Dantoine. Temperature dependence of binding and catalysis for human serum arylesterase/paraoxonase.. Biochimie, 2014, 97, pp.72-77. ⟨10.1016/j.biochi.2013.09.022⟩. ⟨hal-00875973⟩
264 View
669 Download

Altmetric

Share

Gmail Facebook X LinkedIn More