Ab Initio Evaluation of the Free Energy Surfaces for the General Base/Acid Catalyzed Thiolysis of Formamide and the Hydrolysis of Methyl Thiolformate:  A Reference Solution Reaction for Studies of Cysteine Proteases

2001 ◽  
Vol 105 (19) ◽  
pp. 4471-4484 ◽  
Author(s):  
Marek Štrajbl ◽  
Jan Florián ◽  
Arieh Warshel
Keyword(s):  
Free Energy ◽  
Ab Initio ◽  
Cysteine Proteases ◽  
Reference Solution ◽  
General Base ◽  
Acid Catalyzed ◽  
Solution Reaction ◽  
Energy Surfaces ◽  
Hydrolysis Of

Substituent Effects on the Chymotrypsin-Catalyzed Hydrolysis of Specific Ester Substrates

1971 ◽  
Vol 49 (2) ◽  
pp. 210-217 ◽  
Author(s):  
R. E. Williams ◽  
M. L. Bender
Keyword(s):  
Free Energy ◽  
Rate Constants ◽  
Substituent Effects ◽  
Phenyl Group ◽  
Linear Free Energy Relationship ◽  
Acylation Reaction ◽  
General Base ◽  
Linear Free Energy ◽  
Base Mechanism ◽  
Hydrolysis Of

The substituent effect on the chymotrypsin-catalyzed hydrolysis of several phenyl esters of specific substrates has been studied. The second-order acylation rate constants (kcat/Km(app)) obey a linear free energy relationship with ρ = +0.63 for phenyl hippurates and ρ = +0.46 for phenyl N-benzyloxycarbonyl-L-tryptophanates when substituents are introduced into the phenyl group of the ester function. These results further support the previously proposed general acid – general base mechanism for the acylation reaction and the formation of a tetrahedral intermediate in the course of the reaction.

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