Transglycosidase operating by a ping-pong reaction mechanism. Involved in the synthesis of raffinose, a major soluble carbohydrate in seeds, roots and tubers (By similarity). alpha-D-galactosyl-(1->3)-1D-myo-inositol + sucrose = myo-inositol + raffinose By oxidative stress. Belongs to the glycosyl hydrolases 36 family.