Mannose 3-Mannosyl residue

Glycolipid 2-a-mannosyltransferase [EC 2.4.1.131] catalyzes the transfer of an a-o-mannosyl residue from GDP-mannose into a lipid-Unked ohgosaccharide, forming an a-l,2-D-mannosyl-D-mannose hnkage. The two 1,2-linked mannosyl residues in the mammalian hpid-lmked... 

The branched cyclodextrins (CDs, 17 a, 17 b) and their analogues with D-galactosyl and a-D-mannosyl residues (17c, 17d) have also been prepared under mild conditions by the approach depicted in Scheme 6 [24,25]. Selective in situ S-deacetylation and activation was obtained by treatment of peracetylated 1-thioglycoses (10a, 8e, 8g) by cysteamine in the presence of diAioerythritol in HMPA [26]. This method was very efficient for ffie synthesis of branched CDs (17a) (80%), (17b) (60%), and (17c) (85%) when the acceptor molecule (15b) bearing primary iodide was used. However, peracetylated 1-thioa-D-mannose (8f) failed as a donor under these conditions, but tetra-O-acetyl-l-thio-a-mannose (8 b) afforded the expected CD (17d) in high yield (83%). 

A way of reconciling the observed proportions of mannobi-, tri-, and tetra-oses and heterosaccharides,16113 released by guar-seed jS-D-mannanase (from hot-water-soluble carob galactomannan), with this model, would be if the enzyme preferentially hydrolyzes appropriate, unsubstituted d-mannosyl residues (as in 31) then, it would only be able to hydrolyze on the reducing side of a substituted D-mannose (as in 32) if there were a... 

The transfer of the oligosaccharide to protein is followed in vivo by the excision of the D-glucosyl residues the nine D-mannosyl residues present in the transferred oligosaccharide probably remain in the inner core of the D-mannan. However, the possibility that some D-mannosyl residues could be almost simultaneously removed and added cannot be precluded.117,167 Finally, terminal, < -d-(1 - 3)-linked D-mannosyl groups are added to the trimmed, protein-bound oligosaccharide.118 The outer chain of the d-mannan is formed after the inner-core oligosaccharide has been transferred to protein and processed, apparently by direct transfer of D-mannosyl groups from GDP-D-mannose.168 The similarity of the structures of the outer chain... 

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