title: A thermodynamic investigation of the glucose-6-phosphate isomerization.
abstract: In this work, Δ(R)g(+) values for the enzymatic G6P isomerization were determined as a function of the G6P equilibrium molality between 25 °C and 37 °C. The reaction mixtures were buffered at pH=8.5. In contrast to standard literature work, Δ(R)g(+) values were determined from activity-based equilibrium constants instead of molality-based apparent values. This yielded a Δ(R)g(+) value of 2.55±0.05 kJ mol(-1) at 37 °C, independent of the solution pH between 7.5 and 8.5. Furthermore, Δ(R)h(+) was measured at pH=8.5 and 25 °C yielding 12.05±0.2 kJ mol(-1). Accounting for activity coefficients turned out to influence Δ(R)g(+) up to 30% upon increasing the G6P molality. This result was confirmed by predictions using the thermodynamic model ePC-SAFT. Finally, the influence of the buffer and of potassium glutamate as an additive on the reaction equilibrium was measured and predicted with ePC-SAFT in good agreement.
authors.affiliation: Laboratory of Thermodynamics, Department of Biochemical and Chemical Engineering, TU Dortmund, Emil-Figge-Str. 70, 44227 Dortmund, Germany.
authors.forename: Philip
authors.initials: P
authors.lastname: Hoffmann
authors.affiliation: Laboratory of Thermodynamics, Department of Biochemical and Chemical Engineering, TU Dortmund, Emil-Figge-Str. 70, 44227 Dortmund, Germany. Electronic address: christoph.held@bci.tu-dortmund.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Held
authors.affiliation: Department of Environmental Microbiology, UFZ Centre for Environmental Research Leipzig-Halle GmbH, Permoserstr. 15, 04318 Leipzig, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Maskow
authors.affiliation: Laboratory of Thermodynamics, Department of Biochemical and Chemical Engineering, TU Dortmund, Emil-Figge-Str. 70, 44227 Dortmund, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Sadowski
mesh_terms: D019298:Glucose-6-Phosphate / Q000737:chemistry*; D018698:Glutamic Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D007700:Kinetics; D013696:Temperature; D013816:Thermodynamics
chemical_list: D018698:Glutamic Acid; D019298:Glucose-6-Phosphate
keywords: Activity coefficient; Enthalpy of reaction; Gibbs energy of reaction; Glycolysis; Thermodynamic equilibrium constant; ePC-SAFT