Isoglobotriosylceramide

Isoglobotriosylceramide, Gal(α1→3)Gal(β1→4)Glcβ(1→1)Cer, abbreviated as iGb3, is an iso-globo-series of glycosphingolipid, which mysteriously disappeared in most mammals studied (pig, mouse, and human), except trace amount reported in the thymus.^[1]

Isoglobotriosylceramide

Names
IUPAC name N-{(2S,3R,4E)-1-[α-D-Galactopyranosyl-(1→3)-β-D-galactopyranosyl-(1→4)-β-D-glucopyranosyloxy]-3-hydroxyoctadec-4-en-2-yl}acetamide
Systematic IUPAC name N-[(2S,3R,4E)-1-{[(2R,3R,4R,5S,6R)-5-{[(2S,3R,4S,5S,6R)-3,5-dihydroxy-6-(hydroxymethyl)-4-{[(2R,3R,4S,5R,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxy}oxan-2-yl]oxy}-3,4-dihydroxy-6-(hydroxymethyl)oxan-2-yl]oxy}-3-hydroxyoctadec-4-en-2-yl]acetamide
Other names isoglobotriasyl ceramide
Identifiers
3D model (JSmol)	Interactive image
ChEBI	CHEBI:52570
ChemSpider	65322719
KEGG	G00403
PubChem CID	73427372
CompTox Dashboard (EPA)	DTXSID901031605
InChI InChI=1S/C38H69NO18/c1-3-4-5-6-7-8-9-10-11-12-13-14-15-16-23(44)22(39-21(2)43)20-52-36-32(50)30(48)34(26(19-42)55-36)56-38-33(51)35(28(46)25(18-41)54-38)57-37-31(49)29(47)27(45)24(17-40)53-37/h15-16,22-38,40-42,44-51H,3-14,17-20H2,1-2H3,(H,39,43)/b16-15+/t22-,23+,24+,25+,26+,27-,28-,29-,30+,31+,32+,33+,34+,35-,36+,37+,38-/m0/s1 Key: DXXSRTXAOPBLSG-HQKKTFEGSA-N
SMILES CCCCCCCCCCCCC/C=C/[C@H]([C@H](CO[C@H]1[C@@H]([C@H]([C@@H]([C@H](O1)CO)O[C@H]2[C@@H]([C@H]([C@H]([C@H](O2)CO)O)O[C@@H]3[C@@H]([C@H]([C@H]([C@H](O3)CO)O)O)O)O)O)O)NC(=O)C)O
Properties
Chemical formula	C38H69NO18
Molar mass	827.959 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

iGb3 was discovered in canine^[2][3] and rat intestines^[4] among iso-globo-series of glycosphingolipids. First NMR spectrums for standard iGb3 were published by Dr. Tomoya Ogawa.^[5][6]

The physiological function of iGb3 is not clear. It has been identified as a CD1d- presented self-antigen for an innate type of immune cells termed as Natural Killer T (NKT) cells.^{[7][8][9][10]} Extensive biochemical studies by multiple methods including HPLC, mass spectrometry, and NMR did not lead to positive finding of iGb3 in major organs of mouse, pig, and human species,^{[11][12][13][14][15]} except trace amount in thymus and immune cells, suggesting a selection pressure during evolution. Obviously, the immune selection pressure against iGb3 is mechanistically different from the well known anti-alpha-Gal antibodies, which caused the loss of alpha1,3-galactose epitope on glycoproteins in humans, apes, and old world monkeys.^[16] The disappearance of iGb3 in pig and mouse species cannot be attributed to anti-alpha-Gal antibodies which are absent in these animals.