H-1-NMR EVIDENCE THAT SALMONELLA-TYPHIMURIUM SIALIDASE HYDROLYZES SIALOSIDES WITH OVERALL RETENTION OF CONFIGURATION

H-1 NMR spectroscopy has been used to investigate the mechanism of hyd rolysis of the synthetic substrate xy-D-glycero-alpha-D-galacto-2-nonu lopyranosidonic acid using the bacterial sialidase from Salmonella typ himurium. Th e H-1 NMR results clearly demonstrate that the initial pr oduct of the substrate hydrolysis is the alpha-anomer of N-acetyl-D-ne uraminic acid (Neu5Ac). Release of N-acetyl-alpha-D-neuraminic acid as the first product of substrate cleavage is consistent with previous i nvestigations which conclude that both viral and other bacterial siali dases catalyze the hydrolysis of alpha-Neu5Ac ketosides with overall r etention of anomeric configuration.