Pp. Lu et al., SYNTHESIS AND EVALUATION OF THIO-TRISACCHARIDES AS ACCEPTORS FOR N-ACETYLGLUCOSAMINYLTRANSFERASE-V, Canadian journal of chemistry, 75(6), 1997, pp. 790-800
N-Acetylglucosaminyltransferase-V (GlcNAcT-V) transfers a beta-linked
GlcNAc residue from UDP-GlcNAc to the 6-OH group of the alpha Man resi
due in oligosaccharides terminating in the sequence lcpNAc-(1-->2)-alp
ha-D-Manp-(1-->6)-beta-D-Glcp-OR (5, R = (CH2)(7)CH3). The terminal Gl
cNAc moiety may be replaced by a Glc residue to produce trisaccharide
6. Two thio analogs (7, 8) of trisaccharide 6, where the oxygen atoms
in the glycosidic linkages between sugar residues were replaced by sul
fur, were prepared by multistep chemical synthesis that made use of th
e key intermediates 1,2-anhydro-3,4,6-tri-O-benzyl-alpha-D-glucose (10
) and 1,2-anhydro-3,4,6-tri-O-benzyl-beta-D-manno (13) as donors for t
he glycosylations. The thio analogs (7, 8) were kinetically evaluated
as substrates for GlcNAcT-V and found to be accepters with two- to thr
ee-fold increase in V-max but higher K-m values (7, K-m = 376 mu M; 8,
K-m = 300 mu M) than their parent compound 6 (K-m = 111 mu M), which
has the natural oxygen linkage. The thio analogs 7 and 8 could be quan
titatively converted into the expected product tetrasaccharides (27, 2
8) by incubation with GlcNAcT-V and UDP-GlcNAc. The enzymatic results
indicate that GlcNAcT-V tolerates the substitution of the natural oxyg
en linkage of the acceptor by a sulfur linkage.