D-fructose + D-glucose = D-glucono-1,5-lactone + D-sorbitol Binds 1 NADP(+) per subunit. The NADP(+) cannot dissociate. Carbohydrate metabolism; D-sorbitol biosynthesis; D-sorbitol from D-fructose and D-glucose: step 1/1. Homotetramer. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has been experimentally proven. Belongs to the Gfo/Idh/MocA family.