Transglycosidase operating by a ping-pong reaction mechanism. Involved in the synthesis of raffinose, a major soluble carbohydrate in seeds, roots and tubers. Able to utilize D-ononitol and D-pinitol as acceptors. May also act as a glycoside hydrolase. alpha-D-galactosyl-(1->3)-1D-myo-inositol + sucrose = myo-inositol + raffinose Inhibited by 1-deoxygalactonojirimycin. Not inhibited by stachyose. Strong inhibition of the hydrolytic activity by sucrose. partially purified enzyme. Optimum pH is 7.0. Belongs to the glycosyl hydrolases 36 family.