Biomedical Engineering Reference
In-Depth Information
Figure 1.
N-glycan biosynthetic pathway in the endoplasmic reticulum and Golgi
apparatus. N-glycan biosynthesis proceeds through an initial stage of sugar removal by
glucosidase I and II and by various α-mannosidases. Subsequent addition of terminal
branches is achieved by organism specifi c mannosyl- and glycosyltransferases.
similar to higher eukaryotes. Other studies, however, have shown a variety
of mannsoylated N-glycan structures produced on fungal glycoproteins
(Wallis et al. 2001), thus a fi ner dissection of the ER and Golgi glycosidases
and glycosyltransferases is necessary. This is particularly relevant for the
α-1,2-mannosidases and mannosyltransferases.
A common theme in the remodeling of various yeast and fungal
expression systems has been the need to preferentially drive the conversion
of the N-glycans to Man
5
GlcNAc
2
, a gateway N-glycan for all subsequent
processing. The remodeling of the glycosylation pathway in yeasts is
complicated by the fact that these organisms produce highly branched
hypermannosylated structures which can contain up to 200 mannose
