Enzymatic Conversion of D-Glucose to D-Fructose

An enzyme which catalyzes the conversion of D-glucose to D-fructose has been demonstrated in cell-free extracts of Streptomyces phaeochromogenus grown in the presence of D-xylose. The enzyme preparation reacts with D-glucose and D-xylose, but not with other sugars tested. It appears to require magnesium for the maximal activity and the addition of cobaltous ion remarkably intensifies the heat tolerance of the enzyme. The maximal activity occurs at about pH 9.3_??_9.5. Equilibrium is reached when about 52% fructose is present in the reaction mixture. The enzyme has half-maximal activity when the concentration of D-glucose is about 0.3M at pH 9 and 60°C.