Free-Energy Relationship in Enzymes

Warshel, A., Schweins, T. and Fothergill, M. (1994). Linear free energy relationships in enzymes. Theoretical analysis of the reaction of tyrosyl-tRNA synthetase. J. Am. Chem. Soc. 116, 8437-8442... 

Hydrolysis of phosphate esters is one of the fundamental biochemical reactions and a vast amount of research has been devoted to the study of phosphoryl transfer reactions [57-60], both in solution and in enzymes. Despite these efforts there are still ambiguities regarding the interpretation of experimental data (e.g., linear free energy relationships, kinetic isotope effects, crystal structures of enzyme-inhibitor complexes etc.) in terms of detailed reaction mechanisms [21,25,59,60]. Of particular interest has been to determine... 

Schutz, C.N. and Warshel, A. (2004). Analyzing free energy relationships for proton translocations in enzymes carbonic anhydrase revisited. J. Phys. Chem. B 108 (6), 2066-2075... 

Since the coordinates log/Cf and log/<,- are independent of each other, a correlation between log/cf and log/ ,- as in Equation (29) would demonstrate the existence of a linear free energy relationship The demonstration of a linear free energy relationship by this means is not necessary for chemical systems because these usually involve substituent change directly adjacent to the reaction centre the correlation is thus chemically reasonable. Application of Equation (29) is significant when the substituent changes may not be so obviously connected with the reaction centre as in the case of the effect of point mutation on conformational changes in enzymes. 

Variation of Substrate Structure. Whereas linear free energy relationships play a central role in the determination of non-enzymic mechanisms, they are much less important for enzymes, for two reasons. First, enzymes have evolved to bind their natural substrates, and substituents introduced in an attempt merely to alter electron demand at the transition state may have many other interactions with the enzyme protein. The result is very noisy Hammett and Bronsted plots. Whereas conclusions can be drawn from non-enzymic rates varying over a factor of 3, with enzyme reactions, to see any trend above the noise it is usually necessary to have rates ranging over several orders of magnitude. 

ScHUTz, C. N., Warshel, A., Analyzing Free Energy Relationships for Proton Translocations in Enzymes ... 

Barberis S, Quiroga E, Morcelle S et al. (2006) Study of phytoproteases stability in aqueous-organic biphasic systems using linear free energy relationships. J Mol Catal B Enzym 38 95-103... 

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