Porcine liver (2 → 3)-α-sialyltransferase: substrate specificity studies and application of the immobilized enzyme to the synthesis of various sialylated oligosaccharide sequences☆

Abstract In search of substrate analogues for the porcine liver β- d -Gal p-(1 → 3)- d -Gal p- NAc: CMP-Neu5Ac-(2 → 3′)-α-sialyltransferase , three disaccharides β- d -Gal p-(1 → 3)-β- d -Gal p-O- CH 3 (5), β- d -Gal p-(1 → 3)-β- d -(2 -O Ac)-Gal p-O- CH 3 (7) and β- d -Gal p-(1 → 3)-β- d -(2 -O Ac)-Gal p-O- Bn (11) were synthesized and tested with the enzyme. Disaccharide 7 turned out to be a very good substrate allowing a rapid access to the trisaccharide α- Neu5Ac -(2 → 3)-β- d -Gal p-(1 → 3)-β- d -(2 -O Ac)-Gal p-O- CH 3 (13) on a preparative scale using the crude enzyme immobilized on cationic exchanger. Trisaccharide 13 was further exploited, first as a sialyl donor in Trypanosoma cruzi trans -sialidase catalyzed reaction and second through acetolysis reaction as a source for the synthon α-Neu5Ac-(2 → 3)- d -Gal (16).