Catalyzes the ring-opening hydrolysis of 3-dehydro-scyllo-inosose (diketo-inositol) to 5-dehydro-L-gluconate, and thus probably functions in a myo-inositol degradation pathway together with IolG, IolM and IolO. 3-dehydro-scyllo-inosose + H2O = 5-dehydro-L-gluconate + H(+) Binds 2 Zn(2+) ions per subunit. Polyol metabolism; myo-inositol metabolism. Homotrimer. The proposed catalytic mechanism involves two water molecules. The first molecule is bound as a bridge between the two metal ions and attacks the carbonyl carbon of the substrate. The second water molecule, that is bound to metal 1, likely functions as a proton donor in catalysis. Belongs to the creatininase superfamily.