Man GlcNAc

The expected products of a hexosaminidase digest of structure 2 would be two isomers in which either the Man 1-3 or Man 1-6 antennae could be terminated with Gal-GlcNAc-Man (no terminal GlcNAc, and thus not susceptible to hexosaminidase), while the second antennae would be newly terminated with Man after release of the exposed terminal GlcNAc by the hexosaminidase. These two isomers would likely have retention times shorter than structure 2 (Table 2). Because there are no commercially available standards corresponding to these structures, identification by chromatographic retention time alone would not be possible. Use of a mannosidase that could distinguish terminal mannose on the Man 1-3 or Man 1-6 anteimae (29) could confirm the proposed structures. 

Glycosylation of the enzyme varies between 0 and 25 %, the main carbohydrates being GlcNAc, Man, Fuc and Xyl. Most of the oligosaccharides correspond to the high-mannose type [22,23] and, in the case of soybean peroxidase, the structure of the major oligosaccharide, which accounts for 60-65% of the total [22], is ... 

Linked structure, NeuAc(a2-3)Gal(31-3)[NeuAc(a2-6)]GalNac(al-G)Ser/Thr, N-Linked structure, [NeuAc(a2-3)Gal-GlcNAc-Man]2-Man-GlcNAc-GlcNAc-Asn. 

Fig. 2. Oligosaccharide processing reactions occurring in the ERin mammalian cells. N, M, G, Dol, Prot, OST, GI, GII, MI, Mil, and GT stand for GlcNAc, Man, Glc, protein, dolichol, glucosidase I, glucosidase II, mannosidase I, mannosidase II, and UDP-GIc glycoprotein glucosyltransferase, respectively.

Biantennary hybrid, GlcNAc(man)5 from bovine rhodopsin... 

---