2024-03-29T15:59:18Zhttps://repositori.uji.es/oai/requestoai:repositori.uji.es:10234/1214232023-06-28T08:03:06Zcom_10234_7013com_10234_9col_10234_8638
00925njm 22002777a 4500
dc
Luk, Louis Y. P.
author
Ruiz-Pernía, José Javier
author
Dawson, William M.
author
Loveridge, E. Joel
author
Tuñón, Iñaki
author
Moliner, Vicent
author
Allemann, Rudolf K.
author
2014
Catalysis by dihydrofolate reductase from the moderately thermophilic bacterium Geobacillus stearothermophilus (BsDHFR) was investigated by isotope substitution of the enzyme. The enzyme kinetic isotope effect for hydride transfer was close to unity at physiological temperatures but increased with decreasing temperatures to a value of 1.65 at 5 °C. This behavior is opposite to that observed for DHFR from Escherichia coli (EcDHFR), where the enzyme kinetic isotope effect increased slightly with increasing temperature. These experimental results were reproduced in the framework of variational transition-state theory that includes a dynamical recrossing coefficient that varies with the mass of the protein. Our simulations indicate that BsDHFR has greater flexibility than EcDHFR on the ps–ns time scale, which affects the coupling of the environmental motions of the protein to the chemical coordinate and consequently to the recrossing trajectories on the reaction barrier. The intensity of the dynamic coupling in DHFRs is influenced by compensatory temperature-dependent factors, namely the enthalpic barrier needed to achieve an ideal transition-state configuration with minimal nonproductive trajectories and the protein disorder that disrupts the electrostatic preorganization required to stabilize the transition state. Together with our previous studies of other DHFRs, the results presented here provide a general explanation why protein dynamic effects vary between enzymes. Our theoretical treatment demonstrates that these effects can be satisfactorily reproduced by including a transmission coefficient in the rate constant calculation, whose dependence on temperature is affected by the protein flexibility.
LUK, Louis YP, et al. Protein Isotope Effects in Dihydrofolate Reductase From Geobacillus stearothermophilus Show Entropic–Enthalpic Compensatory Effects on the Rate Constant. Journal of the American Chemical Society, 2014, vol. 136, no 49, p. 17317-17323.
0002-7863
1520-5126
http://hdl.handle.net/10234/121423
http://dx.doi.org/10.1021/ja5102536
Dihydrofolate reductase
Geobacillus stearothermophilus
Increasing temperatures
Kinetic isotope effects
Moderately thermophilic
Rate constants
Escherichia coli
Protein Isotope Effects in Dihydrofolate Reductase From Geobacillus stearothermophilus Show Entropic–Enthalpic Compensatory Effects on the Rate Constant