Catalyzes the dehydration of inosose (2-keto-myo-inositol, 2KMI or 2,4,6/3,5-pentahydroxycyclohexanone) to 3D-(3,5/4)-trihydroxycyclohexane-1,2-dione (D-2,3-diketo-4-deoxy-epi-inositol). scyllo-inosose = 3D-3,5/4-trihydroxycyclohexane-1,2-dione + H2O Belongs to the IolE/MocC family.