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A Thermodynamic Investigation of Some Reactions Involving Prephenic Acid



N Kishore, Marcia J. Holden, Yadu D. Tewari, Robert N. Goldberg


Calorimetric enthalpies of reaction have been measured for the following enzyme-catalyzed reactions at the temperature 298.15 Kprephenate(aq) = phenylpyruvate(aq) + H20(l) + carbon dioxide(aq), prephenate(aq) + NADox(aq) = 4-hydroxyphenylpyruvate(aq) + NADred(aq) + carbon dioxide(aq).Here, NADox and NADred are, respectively, the oxidized and reduced forms of β-nicotinamide-adenine dinucleotide. The enzymes that catalyze these respective reactions, prephenate dehydratase and prephenate dehydrogenase, were prepared by expression of the appropriate plasmids and by using the techniques of molecular biology. The calorimetric measurements together with equilibrium modelling calculations lead to a standard molar enthalpy change {Δ}rHmo = -(126 5) kJ mol-1 for the reference reaction:prephenate2-(aq) = phenylpyruvate-(aq) + HCO3-(aq).Similarly, {Δ}rHmo = -(74 3) kJ mol-1 for the reference reactionprephenate2-(aq) + NADox-(aq) + H2O(l) =4-hydroxyphenylpyruvate-(aq) + NADdred2-(aq) + HCO3-(aq) + H+(aq).Both results pertain to T = 298.15 K and ionic strength Im = 0. Benson estimates for the entropies lead to approximate values of the equilibrium constants K {approximately equal to} 1026 and K {approximately equal to} 1012, respectively, for the above two reference reactions.
Journal of Chemical Thermodynamics


4-hydroxyphenylpyruvic acid, enthalpy, phenylpyruvic acid, prephenate dehydratase, prephenate dehydrogenase, prephenic acid, Β-nicotinamide-adenine dinucleotide


Kishore, N. , Holden, M. , Tewari, Y. and Goldberg, R. (1999), A Thermodynamic Investigation of Some Reactions Involving Prephenic Acid, Journal of Chemical Thermodynamics (Accessed April 21, 2024)
Created February 1, 1999, Updated February 17, 2017