Standard molar entropies,standard entropies of formation,and standard transformed entropies of formation in the thermodynamics of enzyme-catalyzed reactions

摘要

The standard transformed Gibbs energy of reaction provides the criterion for spontaneous change and equilibrium for an enzyme-catalyzed reaction at specified temperature,pressure,and pH.The standard transformed enthalpy of reaction yields the heat of reaction.The standard transformed entropy of reaction has received less attention,but it provides almost all of the pH dependence of the apparent equilibrium constant.When the standard Gibbs energies of formation DELTA_fG_j~(deg)(298.15K,I=0)and standard enthalpies of formation DELTA_fH_j~(deg)(298.15 K,7=0)of the species of a reactant are known,the standard entropies of formation DELTA_fS_j~(deg)(298.15 K,I=0)can be calculated.With the database BasicBiochemData2 and recent extensions,this can be done for about fifty reactants.However,standard molar entropies S_m~(deg)(298.15 K,I=0)of species are of more interest because it may be possible to interpret their values and use them to estimate S_m deg values for species for which DELTA_fH_j~(deg) are unknown.These estimates of S_m deg of species for which DELTA_fG_j~(deg) values are known make it possible to obtain DELTA_fH_j~(deg) of species that can be used to calculate effects of temperature on standard transformed Gibbs energies of reactants and apparent equilibrium constants of enzyme-catalyzed reactions.