Enzymatic isomerization kinetics of D-glucose to D-fructose

An investigation into the kinetics of the enzymatic isomerization of D-glucose to D-fructose, employing spectrophotometric techniques, is described. It is shown that the free solution enzymatic catalytic reaction is coupled with the two mutarotation reactions of D-glucose (α, β-D-glucopyranose simple mutarotation) and D-fructose (α, β-D-fructopyranose mutarotation and interconversion with α, β-D-fructofuranose mutarotation). Plausible reaction schemes are suggested and two simplified cases are employed to intarpret the data. Experimental evidence presented herein and previously reported by Schray and Rose appear to indicate that the isomerase is stereospecific to α-D-glucopyranose. The enzymatic interconversion follows Michaelis-Menten kinetics and values of the rate coefficients are presented. Arrhenius temperature dependency is indicated for all rate constants over the temperature range 50 - 80 °C, and energies of activation values are reported.