PORCINE LIVER (2-]3)-ALPHA-SIALYLTRANSFERASE - SUBSTRATE-SPECIFICITY STUDIES AND APPLICATION OF THE IMMOBILIZED ENZYME TO THE SYNTHESIS OF VARIOUS SIALYLATED OLIGOSACCHARIDE SEQUENCES

In search of substrate analogues for the porcine liver beta-D-Galp-(1 --> 3)-D-Galp-NAc: CMP-Neu5Ac-(2 --> 3')-alpha-sialyltransferase, thre e disaccharides beta-D-Galp-(1 --> 3)-beta-D-Galp-O-CH3 (5), beta-D-Ga lp-(1 --> 3)-beta-D-(2-OAc)-Galp-O-CH3 (7) and beta-D-Galp-(1 --> 3)-b eta-D-(2-OAc)-Galp-O-Bn (11) were synthesized and tested with the enzy me. Disaccharide 7 turned out to be a very good substrate allowing a r apid access to the trisaccharide alpha-Neu5Ac-(2 --> 3)-beta-D-Galp-(1 --> 3)-P-D-(2-OAc)-Galp-O-CH3 (13) on a preparative scale using the c rude enzyme immobilized on cationic exchanger. Trisaccharide 13 was fu rther exploited, first as a sialyl donor in Trypanosoma cruzi trans-si alidase catalyzed reaction and second through acetolysis reaction as a source for the synthon alpha-Neu5Ac-(2 --> 3)-D-Gal (16). (C) 1997 El sevier Science Ltd.