TAILIEUCHUNG - Báo cáo khoa học: Rate-determining step of butyrylcholinesterase-catalyzed hydrolysis of benzoylcholine and benzoylthiocholine Volumetric study of wild-type and D70G mutant behaviou

The rate-limiting step for hydrolysis of thepositivelycharged oxoester benzoylcholine (BzCh) by human butyrylcho linesterase (BuChE) is deacylation (k3 ), whereas it is acyla-tion (k2 ) for hydrolysis of the homologous thioester ben-zoylthiocholine (BzSCh). Steady-state hydrolysis of BzCh and BzSCh by wild-type BuChEand its peripheral anionic site mutant D70G was investigated at different hydrostatic pressures, which allowed determination of volume changes associated with substrate binding, and the activation vol-umes for the chemical steps | Eur. J. Biochem. 271 1980-1990 2004 FEBS 2004 doi Rate-determining step of butyrylcholinesterase-catalyzed hydrolysis of benzoylcholine and benzoylthiocholine Volumetric study of wild-type and D70G mutant behaviour Patrick Masson1 Nicole Bec2 Marie-Therese Froment1 Florian Nachon1 3 Claude Balnv2. Oksana Lockridge3 and Lawrence M. Schopfer3 1 Centre de Recherches du Service de Sante des Armees CRSSA Departement de Toxicologie Unite d Enzymologie 38702 La Tronche cedex France 2INSERM U128 34293 Montpellier Cedex 5 France 3 University of Nebraska Medical Center Eppley Institute Omaha NE USA The rate-limiting step for hydrolysis of the positively charged oxoester benzoylcholine BzCh by human butyrylcho linesterase BuChE is deacylation k3 whereas it is acylation k2 for hydrolysis of the homologous thioester benzoylthiocholine BzSCh . Steady-state hydrolysis of BzCh and BzSCh by wild-type BuChE and its periphera 1 anionic site mutant D70G was investigated at different hydrostatic pressures which allowed determination of volume changes associated with substrate binding and the activation volumes for the chemical steps. A differential nonlinear pressure-dependence of the catalytic parameters for hydrolysis of both substrates by both enzymes was shown. Nonlinearity of the plots may be explained in terms of compressibility changes or rate-limiting changes. To distinguish between these two possibilities enzyme phosphorylation by diisopropylfluorophosphate DFP in the presence of substrate BzSCh under pressure was studied. There was no pressure dependence of volume changes for DFP binding or for phosphorylation of either wild-type or D70G. Analysis of the pressure dependence for steady-state hydrolysis of substrates and for phosphorylation by DFP provided evidence that no enzyme compressibility changes occurred during the catalyzed reactions. Thus the nonlinear pressure dependence of substrate hydrolysis reflects changes in the rate-limiting .

• Báo cáo khoa học
• Report medicine
• traditional medicine
• scientific reports
• medical knowledge
• medical research
• analysis of cytoplasmic
• oxidation
• Crystal structure
• bacteria
• hemoglobin
• medicine
• cell proliferation
• breast cancer
• chemical reaction
• gastric cancer
• hormone medicine
• tumor cells
• biochemical studies
• environmental medicine