Studies on Glucose-Isomerizing Enzyme of Bacteria

D-Glucose-isomerizing enzyme from Escherichia intermedia HN-500, which converts D-glucose to D-fructose in the presence of arsenate, was purified by treating with manganous sulfate, rivanol, and DEAE-Sephadex column chromatography. About 180-fold purified enzyme preparation was obtained by the above procedures. The purified preparation was free from the activities of D-glucose-, D-galactose-, glucose-6-phosphate-, mannitol-, and sorbitol- dehydrogenases and was homogeneous on polyacrylamide gel in zone electrophoresis. Optima of pH and temperature for the enzyme were found to be pH 7.0 and 50°C, respec-tively. The enzyme was completely inactivated by heating at 60°C for ten minutes and stable in the pH range of 7.0_??_9.0 at 30°C. Activation energy for the isomerizing enzyme was calculated to be 15, 300 calories per mole-degree from Arrhenius' equation. Either in the absence or presecne of arsenate, D-mannose, D-xylose, D-mannitol and D-sorbitol could not be isomerized by the purified enzyme at all, but the present enzyme isomerized exclu-sively glucose-6-phosphate and fructose-6-phosphate in the absence of arsenate.