4-Methylumbelliferyl glycosides of N-acetyl 4-thiochito-oligosaccharides as fluorogenic substrates for chitodextrinase from Vibrio furnissii

The degradation of chitin involves a diverse array of enzymes, some with overlapping substrate specificities. In order to distinguish between different types of enzymes, specific substrates are needed. Toward this end, two new fluorogenic substrates containing thio-glycosidic linkages, 4-methylumbelliferyl N,N'-diacetyl-4-thio-beta-chitobioside (Mu-TCB) and N,N',N"-triacetyl-4,4'-dithio-beta-chitotrioside (Mu-TCT) are described. The substitution of the glycosidic oxygens (except the one that links oligosaccharide with the fluorogenic aglycon) with a sulfur atom resulted in resistance of these compounds to N-acetyl-beta-hexosaminidases while they were specific substrates for the newly discovered chitodextrinase from Vibrio furnissii (Keyhani,N.O. and Roseman,S. (1996) J. Biol. Chem., 271, 33414-33424) and some bacterial chitinases. The enzyme kinetics of these 4-S-linked substrates, Mu-TCB and Mu-TCT, as well as the O-linked 4-methylumbelliferyl N,N'-diacetyl-beta-chitobioside (Mu-CB) and N,N',N"-triacetyl-beta-chitotrioside (Mu-CT) with the chitodextrinase were studied and compared. The usefulness of the substrates for screening for chitodextrinase and/or chitinase activity was demonstrated.