Chemistry Reference
In-Depth Information
Figure 22.3
Profi ling of LLO by high - pressure
liquid chromatography (HPLC). Fibroblast cells
isolated from a skin biopsy are incubated with
radiolabeled [
3
H]mannose, which is incorpo-
rated into LLO. After extraction from the cells,
LLOs are separated by HPLC and the resulting
profi les are compared to a yeast LLO standard
to identify the type of LLO possibly accumulat-
ing in the cells investigated. In the case of
CDG-Ic (lower panel), the cells accumulate
the incomplete lipid-linked GlcNAc
2
Man
9
(M9)
structure.
(OMIM 606056), represent true defects of
N
- glycosylation (Table 22.1 ). Defi cien-
cies of GDP-Fuc transporter (CDG-IIc, OMIM 266265),
B4GALT1
1,4 - Gal -
transferase - 1 (CDG - IId, OMIM 607091) and CMP - sialic acid ( Sia ) transporter
(CDG-IIf, OMIM 603585) also affect the formation of
O
- glycans and glycolipids.
Defects in the subunits of the COG complex (see below, Section 22.10), which is
involved in vesicular traffi cking, have also been referred to as types of CDG- II
(Table 22.1), since these defects affect
N
- glycosylation. However, multiple glyco-
sylation pathways and possibly other cellular processes are also disturbed in COG
β
