Remarkable Rate Enhancement of Orotidine 5‘-Monophosphate Decarboxylase Is Due to Transition-State Stabilization Rather Than to Ground-State Destabilization†

Biochemistry ◽  
2000 ◽  
Vol 39 (48) ◽  
pp. 14728-14738 ◽  
Author(s):  
Arieh Warshel ◽  
Marek Štrajbl ◽  
Jordi Villà ◽  
Jan Florián
Keyword(s):  
Transition State ◽  
Ground State ◽  
Rate Enhancement ◽  
Transition State Stabilization ◽  
Monophosphate Decarboxylase

Contributions of Conformational Compression and Preferential Transition State Stabilization to the Rate Enhancement by Chorismate Mutase

2003 ◽  
Vol 125 (23) ◽  
pp. 6892-6899 ◽  
Author(s):  
Cristiano Ruch Werneck Guimarães ◽  
Matthew P. Repasky ◽  
Jayaraman Chandrasekhar ◽  
Julian Tirado-Rives ◽  
William L. Jorgensen
Keyword(s):  
Transition State ◽  
Chorismate Mutase ◽  
Rate Enhancement ◽  
Transition State Stabilization

Metal ion catalysis in nucleophilic displacement reactions at carbon, phosphorus, and sulfur centers. I. Catalysis by metal ions in the reaction of p-nitrophenyl diphenylphosphinate with ethoxide

1989 ◽  
Vol 67 (9) ◽  
pp. 1440-1448 ◽  
Author(s):  
Edward J. Dunn ◽  
Erwin Buncel
Keyword(s):  
Crown Ether ◽  
Alkali Metal ◽  
Transition State ◽  
Metal Ions ◽  
Ground State ◽  
Metal Ion ◽  
Complexing Agents ◽  
Transition State Stabilization ◽  
Nucleophilic Displacement ◽  
Metal Ion Catalysis

The effect of macrocyclic crown ether and cryptand complexing agents on the rate of the nucleophilic displacement reaction of p-nitrophenyl diphenylphosphinate by alkali metal ethoxides in ethanol at 25 °C has been studied by spectrophotometric techniques. For the reactions of potassium ethoxide, sodium ethoxide, and lithium ethoxide, the observed rate constant increased in the order KOEt < NaOEt < LiOEt. Crown ether and cryptand cation-complexing agents have a retarding effect on the rate. Increasing the ratio of complexing agent to base results in a decrease in kobs to a minimum value corresponding to the rate of reaction of free ethoxide ion. In complementary experiments, alkali metal ions were added to these reaction systems in the form of unreactive salts, causing an increase in reaction rate. The kinetic data were analysed in terms of ion-pairing treatments, which allowed evaluation of rate coefficients due to free ethoxide ions and metal ion – ethoxide ion pairs. Possible roles of the metal cations are discussed in terms of ground state and transition state stabilization. Evaluation of the equilibrium constants for association of the metal ion with ground state (Ka) and the transition state (K′a) shows that catalysis occurs as a result of enhanced association between the metal ion and the transition state, with (K′a) values increasing in the order K+ < Na+ < Li+. A model is proposed in which transition state stabilization arises largely from chelation of the solvated metal ion to two charged oxygen centers. This appears to be the first reported instance of catalysis by alkali metal cations in nucleophilic displacement at phosphoryl centers. Keywords: nucleophilic displacement at phosphorus, alkali-metal-ion catalysis.

scholarly journals Orotidine 5′-Monophosphate Decarboxylase: Transition State Stabilization from Remote Protein–Phosphodianion Interactions

Biochemistry ◽  
2012 ◽  
Vol 51 (23) ◽  
pp. 4630-4632 ◽  
Author(s):  
Tina L. Amyes ◽  
Shonoi A. Ming ◽  
Lawrence M. Goldman ◽  
B. McKay Wood ◽  
Bijoy J. Desai ◽  
...  
Keyword(s):  
Transition State ◽  
Transition State Stabilization ◽  
Monophosphate Decarboxylase
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