A Thermodynamic Investigation of Some Reactions Involving Prephenic Acid

Published

February 1, 1999

Author(s)

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

Abstract

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) + NAD_ox(aq) = 4-hydroxyphenylpyruvate(aq) + NAD_red(aq) + carbon dioxide(aq).Here, NAD_ox and NAD_red 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}_rH_m^o = -(126 5) kJ mol^-1 for the reference reaction:prephenate^2-(aq) = phenylpyruvate^-(aq) + HCO₃^-(aq).Similarly, {Δ}_rH_m^o = -(74 3) kJ mol^-1 for the reference reactionprephenate^2-(aq) + NAD_ox^-(aq) + H₂O(l) =4-hydroxyphenylpyruvate^-(aq) + NADd_red^2-(aq) + HCO₃^-(aq) + H⁺(aq).Both results pertain to T = 298.15 K and ionic strength I_m = 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.

Citation

Journal of Chemical Thermodynamics

Volume

31

Issue

2

Pub Type

Journals

Keywords

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

Citation

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 23, 2024)