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Chemical characterization of penta-, hexa-, hepta-, octa-, and nonaglycosylceramides of rat small intestine having a globoside-like terminus.

1982; Elsevier BV; Volume: 257; Issue: 2 Linguagem: Inglês

10.1016/s0021-9258(19)68248-7

1083-351X

Jonas Ångström, Michael E. Breimer, K. Falk, Gunnar C. Hansson, K.‐A. Karlsson, Hakon Leffler,

Pancreatic function and diabetes

A novel series of glycosphingolipids has been isolated from the nonepithelial part of rat small intestine.A mixed fraction containing 3 major components corresponding to glycolipids with 5, 6, and 7 sugars and 2 minor components with 8 and 9 sugars was characterized.The structure of the major components was deduced by mass spectrometry and proton NMR spectroscopy of nondegraded permethylated and permethylated-reduced (LiAlH,) derivatives and gas-liquid chromatography of degradation products of native, permethylated, and permethylated-reduced glycolipids.The structures of the penta-, hexa-, and hepta-glycosylceramides were found to be GalNAcpPl + (3Galpal -+)z.44Galp/31+ 4Glcppl .+1Cer.By analogy reasoning, supported by mass spectrometry, the octaand nonaglycosylceramides were concluded to have l and 2 additional internal "-f 3Galpal -3 structures, respectively.A pentaglycosylceramide fraction from another rat strain was also isolated.The NMR spectra were in agreement with 2 isomeric structures of which 1 had the internal a1 -+ 4 linkage replaced by an a1 + 3 linkage.The fatty acids of all components were nonhydroxy 16:O to 24:O acids with the 18:O homologue as dominating species.The major base was sphingosine and possibly monohydroxy 18:l base in the larger glycolipids.This is a novel series of structures with a terminal saccharide identical with isoglobotetraosylceramide (cytolipin R).The glycosyltransferase for the terminal GalNAcpl+ 3 of cytolipin R may possibly be identical with the enzyme adding the terminal sugar of this novel series.This is supported by the presence in the same tissue of probable precursor glycolipids with 4 to 8 hexoses.Glycosphingolipids are constituents of the cell surface membrane and are known to comprise specific immunologic properties (1, 2).Globoside or globotetraosylceramide' (GalNAcPl -+ 3Galal -+ 4GalPl + 4GlcP1 + 1Cer) is the