Calorimetric Glucose Determination by Glucose Oxidase —Methylene Blue

Abstract

The reaction between glucose and mcthylcne blue, catalyzed by glucose oxidase (GOD), was analysed calorimetrically. The amount of heat produced under saturating methylene blue concentrations (> 10-2 mol/l) was measured with glucose concentration and time as parameters (kinetic procedure). Kinetic constants (pseudo one substrate kinetics) were derived from tho experimental data: K M (~~~~~~~) = 1.18x 10-3 mol/l and T, , , = 0.085 J/mg GOD min (3.89 . lo-" mol/mg GOD min).Comparison of caloric with optical measurements gave an enthalpy of reaction of 22.52 kJ/mol. Considering the observed substretc inhibition, glucose determinations arc possible up to glucose concentrations of 0.1 mol/l. ZussmmonfassungDie G1 ukoseoxydase-kstalysierte Reaktion zwischen Glukose und Methylenblau wurde kalorimetrisch verfolgt. Die unter siittigenden Methylenblaukonzentrationen (> lo-* mol/l) gebildeten Warmemengen mirden mit Glukosekonzentration und Zeit als Parametern bestimmt (kinetisches Verfahren). Die Experimente ergaben folgende kinetische Daten (Pseudo-Einsubstratkinetik) : KM(Glukose) = 1,18 . 10-3 mol/l und V,,, = 0,085 J/mg GODmin (3,89 -10-6 mol/mg GODmin).Der Vergleich der kalorischen mit optischen Messungen ergab eine Reaktionsenthblpie von 22,52 kJ/mol. Unter Berucksichtigung der beobachteten SubstratuberschuBhemmung sind Glukosebestimmungen bis zu 0,l mol/l moglich.

The Blue Bottle Experiment Revisited: How Blue? How Sweet?

“…where D is the reduced (colorless) form of the dye methylene blue, and Xrepresents the oxidation products from the glucose (arabinoic, formic, oxalic, and erythronic acids (3,4)). The enthalpy of the reaction has been reported to be 5.5 kcal/mol (5).…”

The methylene blue-D-glucose-O2 system. Oxidation of D-glucose by methylene blue in the presence and the absence of oxygen

“…A saturation curve was obtained by plotting the k obs values, or the initial rates, against [glucose], for the given concentration of NaOH. A similar saturation curve from the reaction between glucose and MB ϩ , catalyzed by glucose oxidase was analyzed calorimetrically [14]. The dependence on the concentration of NaOH was determined for 0.08 M and 0.25 M glucose.…”