Chemistry Reference
In-Depth Information
Table 10.3
Examples for the S vennerholm designation of gangliosides
(for detailed information on structural and biosynthetic aspects, please
see Figure 30.3 ).
Svennerholm designation
Abbreviated structure
GM3
II
3
NeuAc - LacCer
II
3
NeuAc - GgOse
3
Cer
GM2
GM1
II
3
NeuAc - GgOse
4
Cer
II
3
(NeuAc)
2
- LacCer
GD3
GD2
II
3
(NeuAc)
2
- GgOse
3
Cer
IV
3
NeuAc,II
3
NeuAc - GgOse
4
Cer
GD1a
GD1b
II
3
(NeuAc)
2
- GgOse
4
Cer
GT1a
IV
3
(NeuAc)
2
,II
3
NeuAc - GgOse
4
Cer
GT1b
IV
3
NeuAc,II
3
(NeuAc)
2
- GgOse
4
Cer
GT1c
II
3
(NeuAc)
3
- GgOse
4
Cer
GQ1b
IV
3
(NeuAc)
2
,II
3
(NeuAc)
2
- GgOse
4
gangliosides belong to the gangliotetraose series, but also globo or lacto series
members may occur. Principles of naming of GSLs as described above are also
applied to gangliosides. Thus, gangliosides are designated as
N
- acetylneuraminyl
(or
N
-glycolylneuraminyl) derivatives of the corresponding neutral oligosaccharide
structure. The site of the sialosyl residue is indicated by a Roman numeral desig-
nating the position of the parent oligosaccharide to which the sialosyl residue is
attached. An Arabic numeral superscript specifi es the position within the parent
chain oligosaccharide to which the sialic acid is attached (Table 10.3). For its sim-
plicity, although being less systematic in structural terms, the Svennerholm des-
ignation for gangliosides is often preferred. Therefore, this nomenclature (Table
10.3) is that encountered most often in the literature. In this system, the letter G
indicates that we deal with gangliosides. The number of sialic acids is indicated
by M = monosialo - , D = disialo - , T = trisialo - and Q = quatrosialo - . The length of
the neutral sugar chain is designated by a number following the formula 5
n
,
where
n
equals the number of neutral sugars in the ganglioside. The position of
the sialic acid(s) can be further characterized by a, b or c, indicating the biosyn-
thetic pathway for the ganglioside (for further details, see Figure 30.3 ). Based on
recommendations of the IUPAC using subscripts, like G
M1
, G
M2
, G
D1a
and so on,
should no longer be used [1]. Structure and chemical properties of GSL establish
the basis for their functions, as will be shown in the next paragraphs.
−
10.8
Survey of GSL Functions
GSLs are always found in the exoplasmic leafl et of membranes and are positioned,
mainly but not exclusively (for functions of GM1 in the nuclear envelope, please
