A H-1-NMR INVESTIGATION OF THE HYDROLYSIS OF A SYNTHETIC SUBSTRATE BYKDN-SIALIDASE FROM CRASSOSTREA-VIRGINICA

The mechanism of hydrolysis of 4-methylumbelliferyl xy-D-glycero-alpha -D-galacto-2-nonulopyranosidonic acid (KDN alpha 2MeUmb, 4) by KDN-sia lidase isolated from the hepatopancreas of the oyster Crassostrea virg inica has been monitored by H-1 NMR spectroscopy. The results of these experiments reveal that KDN-sialidase catalyses the hydrolysis of the synthetic substrate KDN alpha 2MeUmb, with initial release of alpha-D -KDN. This is consistent with an overall mechanism for the hydrolysis which proceeds with retention of anomeric configuration. These results agree with earlier NMR studies of other N-acetylneuraminic acid-recog nising sialidases from both viral and bacterial sources.