Abstract
The activity ratio of glucose isomerization to glucose-6-phosphate isomerization was practically constant during the course of purification of the enzyme, and it was impossible to separate the two isomerizing activities by means of Sephadex G-150 and DEAE-Sephadex column chromatographies. Furthermore, the similarlity in pH stability and thermal stability, and the competitive inhibition by 6-phosphogluconate were observed in both isomerizing reactions. In kinetic experiments, however, Michaelis constants (Km) were calculated to be 1.6M for the arsenate-requiring glucose isomerization, and 1.4×10-3M for the glucose-6-phosphate isomerization. These results indicate that the arsenate-requir-ing glucose- and the arsenate-independent glucose-6-phosphate-isomerizing reactions are catalyzed by the same enzyme, and that the glucose-isomerizing enzyme is a glucose phosphate isomerase itself.
