Involved in the oxidation of myo-inositol (MI) and D-chiro-inositol (DCI) to 2-keto-myo-inositol (2KMI or 2-inosose) and 1-keto-D-chiro-inositol (1KDCI), respectively. Can also use D-glucose and D-xylose, and shows a trace of activity with D-ribose and D-fructose. myo-inositol + NAD(+) = H(+) + NADH + scyllo-inosose 1D-chiro-inositol + NAD(+) = H(+) + NADH + scyllo-inosine Optimum pH is 9.5 for inositol 2-dehydrogenase activity. Polyol metabolism; myo-inositol degradation into acetyl-CoA; acetyl-CoA from myo-inositol: step 1/7. Homotetramer. By inositol. Subjected to catabolite repression. Belongs to the Gfo/Idh/MocA family.