Download O-Linked Glycoproteins - Sigma

GLY FINAL 1207 PGD cleanxrefs2
O-Glycans
O-Glycans
O-Linked glycoproteins are usually large proteins with a molecular mass of >200 kDa. Glycosylation generally occurs in high-density clusters and may
represent as much as 50‑80% of the overall mass.
O-Linked glycans are most commonly attached to the peptide chain through serine (Ser) or threonine (Thr) residues. While O-linkage does link
primarily to peptide residues through a hydroxyl group, there is no consensus sequence required. Tyrosine (Tyr), hydroxylysine (Hydroxy-Lys), or
hydroxyproline (Hydroxy-Pro) may also be the peptide site of O-linked glycosylation.
The most common O-linked glycans are the mucin-type glycans, which contain an initial GalNAc residue. There are eight mucin-type core structures
(see Figure 6). Even with common mucin-type cores, O-linked glycans tend to be very heterogeneous, and there are other structures possible, in
addition to several sialylated core structures. However, O-linked glycans are commonly linear or biantennary and have comparatively less branching
than N-glycans.
β1,3
Ser/
Thr
Core 1
β1,6
β1,3
Ser/
Thr
Core 2
β1,3
Ser/
Thr
Core 3
β1,6
β1,3
Ser/
Thr
Core 4
α1,3
Ser/
Thr
Core 5
Glycan Component Classes
Structures
Mucins are glycoproteins that contain large numbers of high-density
clusters of O-linked glycans. The mucin-type glycans of these proteins
frequently form cross-linked connections in aqueous solutions, resulting
in a high viscosity gel (mucus). Mucins can be secreted, but may also be
membrane bound and form glycan-dense areas on the cell surface.
In addition to mucin-type glycans, O-linked glycans may incorporate
sugars other than GalNAc as the initial sugar bound to the serine/
threonine residues. Examples of alternative O-linked glycans are:
• Nuclear and cytoplasmic glycoproteins that contain GlcNAc as the
initiating sugar.
• Fibrinolytic and coagulation factors that contain fucose as the initiating
sugar.
• Mannoproteins that are typical to yeasts and that incorporate
mannose as the initiating sugar. O-Mannosyl glycans are also found in
human α-dystroglycan and other nervous system glycoproteins.
• Glycosaminoglycans (GAGs) that are components of proteoglycan
structures and contain xylose bound exclusively to serine residues.
• Plant cell wall extensins that contain both arabinose attached to
hydroxyproline and galactose attached to serine.
• Plant arabinogalactans that are attached to the hydroxyproline within
the peptide backbone through O-linked galactose or glucose.
• Galactose and αGlc(1→2)Gal residues that are bound to hydroxylysine
within the triple helix structures of collagen. Complement factor C1q
also contains αGlc(1→2)Gal-hydroxyproline sequences.
• Glycogenin, a protein precursor required for glycogen synthesis,
contains glucose O-linked to tyrosine; the initial glucose is subsequently elongated by glycogen synthase to generate glycogen.
Key to Monosaccharide Symbols
β1,6
Ser/
Thr
Core 6
α1,6
β-D-Glucose (Glc)
β-D-Xylose (Xyl)
β-D-Mannose (Man)
α-N-Acetylneuraminic acid;
Sialic acid (NeuNAc)
β-D-Galactose (Gal)
β-D-Glucuronic acid (GlcA)
β-D-N-Acetylglucosamine (GlcNAc)
α-L-Iduronic acid (IdoA)
β-D-N-Acetylgalactosamine (GalNAc)
α-L-Fucose (Fuc)
Ser/
Thr
Core 7
α1,3
Core 8
Ser/
Thr
Figure 6. Core structures of mucin-type O-glycans.
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GLY FINAL 1207 PGD cleanxrefs2
O-Glycans
Glycan Component Classes
Biosynthesis and Degradation
O-linked glycosylation is a true post-translational event that occurs in the
Golgi, and no oligosaccharide precursor is required for protein transfer.
The serine/threonine residues are modified directly by covalent addition
of N-acetylgalactosamine residues. Initiation of mucin-type O-glycosylation is dependent upon polypeptide N-acetylgalactosyl transferase
(ppGalNAcT); at least twelve mammalian ppGalNAcT isozymes have
been identified. The first step in the synthesis of mucin-type glycans
requires catalysis by a ppGalNAcT in the presence of UDP-GalNAc as the
carbohydrate donor. Subsequent elongation and termination of O-linked
glycans is carried out by several glycosyltransferases. The relative
expression and subcellular distribution of the various glycosyltransferases
determine the outcome of O-glycan biosynthesis. For additional
discussion of Glycosyltransferases, see page 87. Termination of
O-linked glycans usually includes Gal, GlcNAc, GalNAc, Fuc, or sialic
acid. By far the most common modification of the core Gal-β(1→3)GalNAc is mono-, di-, or trisialylation (Core 1 and 2) (see Figure 7). A
less common, but widely distributed O-linked hexasaccharide structure
contains β(1→4)-linked Gal and β(1→6)-linked GlcNAc, as well as sialic
acid.
α2,3
More complex O-glycans serve other functions. ZP glycoproteins are
O-linked glycans present in high concentrations in the zona pellucida
surrounding mammalian eggs. Human ZP matrix contains four ZP
glycoproteins, while the mouse ZP matrix has only three.3 The roles of ZP
glycoproteins have not been fully determined but are thought to be
associated with sperm reception.
O-Linked glycans are also involved in hematopoiesis and inflammation
response mechanisms. The P-selectin glycoprotein ligand 1 (PSGL-1)
contains, among other glycans, a Core 2 O-glycan capped with sialyl
Lewis X (C2‑O-sLeX, see Figure 8). PSGL-1 is the primary adhesion target
for P-selectin and a target for E-selectin, which are involved in leukocyte
rolling and recruitment into sites of inflammation.4
β1,4
α2,3
β1,3
β1,4
β1,3
β1,4
α1,3
β1,6
β1,3
β1,3
Ser/
Thr
α2,6
α2,3
Proteins that are O-linked with GlcNAc may alternatively be phosphorylated at the same peptide site, and similarly to phosphorylation,
O-GlcNAc processing has been associated with cellular signaling events,
including insulin signaling and RNA transcription regulation.1,2
β1,3
Ser/
Thr
Figure 8. Structure of the O-linked Core 2 glycan with attached sialyl Lewis X (sLex)
moiety.
Ser/
Thr
α2,6
The human ABO blood antigens are small O-linked glycans that may be
attached to membrane glycoproteins or to cell surface glycolipids. The
antigens may also be secreted by tissues as free oligosaccharides or as
components of soluble glycoproteins and glycosphingolipids. The blood
group O(H) determinant does not generate an immune response, but
when modified by addition of either α(1→3)GalNAc (blood group A
antigen) or α(1→3)Gal (blood group B antigen), the resultant
trisaccharide initiates an immune response (see Figure 9).
α2,8
α1,2
Figure 7. Disialylated (top) and trisialylated (bottom) O-linked Core 1 glycans
O-glycan degradation requires α-N-acetylgalactosaminidase in addition
to the same exoglycosidases needed for N-glycan degradation.
β1,0
R
A
Functions
Secreted mucins at the apical membrane of epithelial cells can link
through disulfide bonds and capture water molecules, forming a mucus
membrane. The membrane physically protects the cell from hostile
environmental factors such as stomach acids and circulating proteases.
Mucin secretion by salivary glands provides lubrication for swallowing.
Mucins also block infection by pathogens by presenting a wall of
O-linked glycans to attract and bind bacterial carbohydrate binding
receptors. Many bacterial pathogens express adhesins, carbohydraterecognition proteins specific for cell surface O-glycan structures that
function as receptors for binding and infecting host cells. The adhesins
bind to the mucin surface glycans, preventing further progress by the
pathogen; the bound pathogen can then be eliminated.
α1,2
α1,3
β1,0
R
B
α1,2
α1,3
β1,0
R
C
Glycosylation by a single GlcNAc moiety is a unique form of
O-glycosylation, in that it has been shown to be dynamic, rather than
static like other types of O-linked glycosylation. This modification is
reversible and catalyzed by the enzymes uridine diphospho-N-acetylglucosmine:polypeptide β-N-acetylglucosaminyltransferase (O-GlcNAc
transferase) and neutral β-N-acetylglucosaminidase (O-GlcNAcase).
14
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Figure 9. Structures of (A) blood group H(O), (B) blood group A, and (C) blood group
B antigens. R represents the hydroxyl-containing amino acid or lipid binding site for
the antigen.
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GLY FINAL 1207 PGD cleanxrefs2
O-Glycans
Lacto-N-difucohexaose I
α-L-Fuc-(1→2)-β-D-Gal-(1→3)[α-L-Fuc-(1→4)]-β-D-GlcNAc-(1→3)-β-D-Gal(1→4)-D-Glc; Leb-lactose; Lewis-b hexasaccharide; LNDFH I
C38H65NO29 FW 999.91 [16789‑38‑1]
 from human milk, ≥95% (HPAE/PAD)
Blood group Leb active hexasaccharide.
store at: 2-8°C
Schindler's Disease has been identified as a congenital disorder of
glycosylation that affects O-linked glycans and is due to an α-Nacetylgalactosaminidase deficiency.
References:
1. Slawson, C., et al., O-GlcNAc cycling: how a single sugar post-translational
modification is changing the way we think about signaling networks. J. Cell. Biochem.,
97, 71‑83 (2006).
2. Wells, L., and Hart, G.W., O-GlcNAc turns twenty: functional implications for posttranslational modification of nuclear and cytosolic proteins with a sugar. FEBS Lett., 546,
154‑8 (2003).
3. Gupta, S.K., et al., Structural and functional attributes of zona pellucida glycoproteins.
Soc. Reprod. Fertil. Suppl., 63, 203‑16 (2007).
4. Sperandio, M., Selectins and glycosyltransferases in leukocyte rolling in vivo. FEBS J.,
273, 4377‑4389 (2006).
α1
2
β1 3
α1
4
β1 3
L7033-1MG
β1 4
Glycan Component Classes
T antigen and Tn antigen are O-glycans that have incomplete
glycosylation. T antigen (tumor-associated or TF (Thomsen-Fridenreich)
antigen) is the Core 1 disaccharide (Gal-β(1→3)GalNAc) that results
after desialylation by viral or bacterial neuraminidase. T antigen may also
result due to changes in the glycosyltransferases available. Tn antigen is
an O-linked GalNAc that is not extended by a glycosyltransferase into a
complete core structure. These antigens are not expressed on the
surface of normal cells, but are commonly present in cancerous cells and
may serve as tumor markers.
1 mg
Lacto-N-difucohexaose II
β-D-Gal-(1→3)-[α-L-Fuc-(1→4)]-β-D-GlcNAc-(1→3)-β-D-Gal-(1→4)-[α-L-Fuc(1→3)]-D-Glc; LNH
C38H65NO29 FW 999.91 [62258‑12‑2]
 from human milk, ~95%
Lewis-a trisaccharide linked to 3‑fucosyllactose
O-Linked Neutral Glycans
store at: 2-8°C
N-Acetyl-D-lactosamine
2‑Acetamido-2‑deoxy-4‑O-β-D-galactopyranosyl-D-glucopyranose; N-Acetyl4‑O-(β-D-galactopyranosyl)-D-glucosamine; β-D-Gal-(1→4)-D-GlcNAc; LN
C14H25NO11 FW 383.35 [32181‑59‑2]
 ≥98%
Useful in studies of galactosidase, fucosyltransferase, sialyltransferase,
and lectin inhibition.
Synthetic
β1 3
α1
4
L6645-.5MG
β1 3
α1
3
β1 4
0.5 mg
store at: −20°C
β1 4
A7791-5MG
5 mg
A7791-10MG
10 mg
A7791-25MG
25 mg
A7791-100MG
100 mg
2′-Fucosyl-D-lactose
Key to Monosaccharide Symbols
α-L-Fuc-(1→2)-β-D-Gal-(1→4)-D-Glc
C18H32O15 FW 488.44 [41263‑94‑9]
 from human milk, ~98% (HPAE/PAD)
β-D-Glucose (Glc)
β-D-Xylose (Xyl)
β-D-Mannose (Man)
α-N-Acetylneuraminic acid;
Sialic acid (NeuNAc)
β-D-Galactose (Gal)
β-D-Glucuronic acid (GlcA)
β-D-N-Acetylglucosamine (GlcNAc)
α-L-Iduronic acid (IdoA)
β-D-N-Acetylgalactosamine (GalNAc)
α-L-Fucose (Fuc)
store at: 2-8°C
2
β
4
F0393-1MG
1 mg
F0393-5MG
5 mg
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GLY FINAL 1207 PGD cleanxrefs2
O-Glycans
O-Linked Sialylated Glycans
Glycan Component Classes
Lacto-N-fucopentaose I
α-L-Fuc (1→2)-β-D-Gal-(1→3)-β-D-GlcNAc-(1→3)-β-D-Gal-(1→4)-D-Glc;
LNFP I
C32H55NO25 FW 853.77 [7578‑25‑8]
3′-N-Acetylneuraminyl-N-acetyllactosamine sodium salt
α-NeuNAc-(2→3)-β-D-Gal-(1→4)-D-GlcNAc; 3′-Sialyl-N-acetyllactosamine; 3′SLN
C25H42N2O19 FW 674.60 [81693‑22‑3]
 from human milk, ≥90% (HPAE/PAD)
Blood group H-active pentasaccharide.
store at: −20°C
store at: 2-8°C
α2
α1
2
β1 3
β1 3
β1 4
3
β1 4
A6936-.5MG
0.5 mg
A6936-2MG
2 mg
3'-Sialyllactose
L5908-5MG
5 mg
3′-N-Acetylneuraminyl-D-lactose sodium salt; NANA-Lactose; α-NeuNAc(2→3)-β-D-Gal-(1→4)-D-Glc; 3'-Sialyl-D-lactose; 3'-SL
C23H39NO19 FW 633.55 [35890‑38‑1]
Lacto-N-fucopentaose III
β-D-Gal-(1→4)-[α-L-Fuc-(1→3)]-β-D-GlcNAc-(1→3)-β-D-Gal-(1→4)-D-Glc; Lexlactose; Lewis-X pentasaccharide; LNFP III
C32H55NO25 FW 853.77 [25541‑09‑7]
 from human milk, ≥95% (HPAE)
α2,3
β1,4
 from human milk, ≥98% (HPAE/PAD)
store at: 2-8°C
store at: −20°C
A9079-1MG
α1,3
β1 4
1 mg
 from bovine colostrum, ~98% (HPAE/PAD)
β1 3
store at: −20°C
β1 4
A8681-1MG
L7777-1MG
1 mg
6′-Sialyllactose sodium salt
1 mg
6′-N-Acetylneuraminyl-lactose sodium salt; α-NeuNAc-(2→6)-β-D-Gal-(1→4)D-Glc; 6'-SL
C23H38NO19Na FW 655.53 [74609‑39‑5]
Lacto-N-tetraose
β-D-Gal-(1→3)-β-D-GlcNAc-(1→3)-β-D-Gal-(1→4)-D-Glc; LNT
C26H45NO21 FW 707.63 [14116‑68‑8]
α2,6
β1,4
 from human milk, ≥95% (HPAE/PAD)
store at: 2-8°C
β
3
β
3
β
 from human milk, ≥95% (HPAE/PAD)
4
store at: −20°C
L6770-1MG
1 mg
L6770-5MG
5 mg
Lacto-N-neo-tetraose
1 mg
A9204-5MG
5 mg
 from bovine colostrum, ≥97% (HPAE/PAD)
8
β-D-Gal-(1→4)-β-D-GlcNAc-(1→3)-β-D-Gal-(1→4)-D-Glc; LNnT
C26H45NO21 FW 707.63 [13007‑32‑4]
A9204-1MG
store at: −20°C
A8556-1MG
1 mg
A8556-5MG
5 mg
 from synthetic, ≥85% (HPLC)
store at: 2-8°C
L6543-2MG
16
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2 mg
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GLY FINAL 1207 PGD cleanxrefs2
O-Glycans
Globotriose
Sialyllactose sodium salt
4‑O-(4‑O-α-D-Galactopyranosyl-β-D-galactopyranosyl)-D-glucopyranose; α-DGal-(1→4)-β-D-Gal-(1→4)-D-Glc
C18H32O16 FW 504.44 [66580‑68‑5]
Mixture of (2→6′) and (2→3′) isomers.
store at: 2-8°C
α2 3/6
β1
α1
4
β1 4
4
G9287-.5MG
 ~80% (HPAE/PAD), from bovine colostrum
iso-A-Pentasaccharide
store at: −20°C
A3307-5MG
5 mg
A3307-25MG
25 mg
α-GalNAc-(1→3)-(α-Fuc-[1→2])-β-Gal-(1→3)-(α-Fuc-[1→4])-Glc; A-LebPentasaccharide
C32H55NO24 FW 837.77 [128464‑25‑5]
 from human milk, ≥97%
store at: −20°C
A0828-5MG
5 mg
A0828-25MG
25 mg
0.5 mg
Glycan Component Classes
N-Acetylneuraminyl-lactose; α-NeuNAc-(2→3)- and -(2→6)-β-D-Gal-(1→4)D-Glc; Neuramin-lactose
C23H38NO19Na FW 655.53
 from human urine, ≥90%
store at: 2-8°C
α1
Blood Group Antigens
α1 3
4β-Galactobiose
4‑O-β-D-Galactopyranosyl-D-galactopyranose; β-D-Gal-(1→4)-D-Gal
C12H22O11 FW 342.30 [2152‑98‑9]
 ≥90%
2
α1
4
β1 3
20 μg
A7560-20UG
B-Pentasaccharide
store at: 2-8°C
α-Fuc-(1→2)-α-Gal-(1→3)-β-Gal-(1→4)(α-Fuc-[1→3])-Glc
C30H52O24 FW 796.72 [72468‑43‑0]
β1 4
G9662-2MG
2 mg
G9662-10MG
10 mg
 from human urine, ≥85%
store at: 2-8°C
Galacto-N-biose
α1
2
2‑Acetamido-2‑deoxy-3‑O-β-D-galactopyranosyl-D-galactopyranose; T
Antigen; β-D-Gal-(1→3)-D-GalNAc
C14H25NO11 FW 383.35 [20972‑29‑6]
A substrate for N-acetylglucosaminyltransferase,1 fucosyl- and
sialyltransferase,2,3 and galactosidase.4 Also used in lectin inhibition
studies.5
Lit. cited: 1. Williams, D., et al., J. Biol. Chem. 255, 11253 (1980)
2. Beyer, T.A. and Hill, R.L., J. Biol. Chem. 255, 5373 (1980)
3. Rearick, J.I., et al., J. Biol. Chem. 254, 4444 (1979)
4. Distler, J.J. and Jourdian, G.W., J. Biol. Chem. 248, 6772 (1973)
5. Tollefsen, S.E. and Kornfeld, R., J. Biol. Chem. 258, 5172 (1983)
α1 3
α1
3
β1 4
50 μg
B3791-50UG
Key to Monosaccharide Symbols
store at: −20°C
β1 3
A0167-1MG
1 mg
A0167-5MG
5 mg
β-D-Glucose (Glc)
β-D-Xylose (Xyl)
β-D-Mannose (Man)
α-N-Acetylneuraminic acid;
Sialic acid (NeuNAc)
β-D-Galactose (Gal)
β-D-Glucuronic acid (GlcA)
β-D-N-Acetylglucosamine (GlcNAc)
α-L-Iduronic acid (IdoA)
β-D-N-Acetylgalactosamine (GalNAc)
α-L-Fucose (Fuc)
Proteomics, glycosylation and other post-translational modifications, visit sigma.com/proteomics
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GLY FINAL 1207 PGD cleanxrefs2
O-Glycans
Lewis and Cell Adhesion Glycans
Glycan Component Classes
iso-B-Pentasaccharide
BLeb-Pentasaccharide; α-Gal-(1→3)-(α-Fuc-[1→2])-β-Gal-(1→3)-(α-Fuc[1→4])-Glc
C30H52O24 FW 796.72 [128464‑26‑6]
 from human urine, ≥85%
Lewis-b tetrasaccharide
α-Fuc(1→2)-β-Gal-(1→3)-(α-Fuc-[1→4])-GlcNAc; Leb glycan
C26H45NO19 FW 675.63
Lewis-b human blood group determinant.
store at: 2-8°C
store at: −20°C
α1
2
α1 3
α1
4
3
β1
20 μg
B0799-20UG
A-Trisaccharide
α1
2
β1 3
α1
4
L7659-1MG
1 mg
Lewis-Y hexasaccharide
Blood group A trisaccharide; α-D-GalNAc-(1→3)-(α-L-Fuc-[1→2])-D-Gal
C20H35NO15 FW 529.49 [49777‑13‑1]
store at: room temp
α-Fuc-(1→2)-β-Gal-(1→4)(α-Fuc-[1→3])-β-GlcNAc-(1→3)-β-Gal-(1→4)-Glc;
Lacto-N-neo-difucohexaose I; Ley-lactose
C38H65NO29 FW 999.91 [62469‑99‑2]
 from human urine
store at: 2-8°C
α1
2
α1 3
α1
2
250 μg
A7911-250UG
β1 4
α1
3
β1 3
B-Trisaccharide
20 μg
L7401-20UG
Blood group B trisaccharide; α-D-Gal-(1→3)-(α-L-Fuc-[1→2])-D-Gal
C18H32O15 FW 488.44 [49777‑14‑2]
store at: 2-8°C
β1 4
Lewis-Y tetrasaccharide
α-Fuc-(1→2)-β-Gal-(1→4)-(α-Fuc-[1→3])-GlcNAc
C26H45NO19 FW 675.63
Lewis-Y blood group antigenic determinant.
α1
2
α1 3
B1422-1MG
store at: 2-8°C
α1
2
1 mg
β1 4
α1
3
H-Trisaccharide
Blood group H trisaccharide; α-Fuc-(1→2)-β-Gal-(1→4)-GlcNAc; 2′-FucosylN-acetyllactosamine
C20H35NO15 FW 529.49
L7784-1MG
 synthetic
Human blood group H type trisaccharide.
store at: 2-8°C
α1
2
F7297-1MG
18
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β1 4
1 mg
For Technical Service, call your local office or visit sigma.com/techinfo
1 mg
GLY FINAL 1207 PGD cleanxrefs2
O-Glycans
α-Gal-(1→3)-Gal Antigens
3′-Sialyl-Lewis-a tetrasaccharide
α-NeuNAc-(2→3)-β-D-Gal-(1→3)-(α-L-Fuc-[1→4])-D-GlcNAc; 3'-SLea
C31H52N2O23 FW 820.74 [92448‑22‑1]
3‑O-α-D-Galactopyranosyl-D-galactose; α-D-Gal-(1→3)-D-Gal
C12H22O11 FW 342.30 [13168‑24‑6]
 synthetic, ≥90%
α2
3
β1 3
store at: 2-8°C
α1
4
α1
S2279-.2MG
0.2 mg
S2279-1MG
1 mg
G7522-5MG
5 mg
3α,4β,3α-Galactotetraose
3′-Sialyl-Lewis-X tetrasaccharide
α-NeuNAc-(2→3)-β-D-Gal-(1→4)(α-L-Fuc-[1→3])-D-GlcNAc; 3'-SLeX
C31H52N2O23 FW 820.74 [98603‑84‑0]
store at: −20°C
3
Glycan Component Classes
store at: −20°C
3‑α-Galactobiose
3‑O-(4‑O-[3‑O-α-D-Galactopyranosyl-β-D-galactopyranosyl]-α-D-galactopyranosyl)-D-galactopyranose; α-D-Gal-(1→3)-β-D-Gal-(1→4)-α-D-Gal-(1→3)D-Gal
C24H42O21 FW 666.58 [56038‑38‑1]
 ≥90%
store at: −20°C
α2
3
β1 4
α1
α1
3
3
G9912-2MG
S1782-.2MG
0.2 mg
S1782-1MG
1 mg
β1 4
α1 3
2 mg
Key to Monosaccharide Symbols
β-D-Glucose (Glc)
β-D-Xylose (Xyl)
β-D-Mannose (Man)
α-N-Acetylneuraminic acid;
Sialic acid (NeuNAc)
β-D-Galactose (Gal)
β-D-Glucuronic acid (GlcA)
β-D-N-Acetylglucosamine (GlcNAc)
α-L-Iduronic acid (IdoA)
β-D-N-Acetylgalactosamine (GalNAc)
α-L-Fucose (Fuc)
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19