Immunochemistry of the Lewis-blood-group system: mass spectrometric analysis of permethylated Le(a)-, Le(b)-, and H-type 1 (LedH) blood-group active and related glycosphingolipids from human plasma

The Structural Diversity of Natural Glycosphingolipids (GSLs)

Glycosphingolipids (GSLs) are a subclass of glycolipids made of a glycan and a ceramide that, in turn, is composed of a sphingoid base moiety and a fatty acyl group. GSLs represent the vast majority of glycolipids in eukaryotes, and as an essential component of the cell membrane, they play an important role in many biological and pathological processes. Therefore, they are useful targets for the development of novel diagnostic and therapeutic methods for human diseases. Since sphingosine was first described by J. L. Thudichum in 1884, several hundred GSL species, not including their diverse lipid forms that can further amplify the number of individual GSLs by many folds, have been isolated from natural sources and structurally characterized. This review tries to provide a comprehensive survey of the major GSL species, especially those with distinct glycan structures and modification patterns, and the ceramides with unique modifications of the lipid chains, that have been discovered to date. In particular, this review is focused on GSLs from eukaryotic species. This review has listed 251 GSL glycans with different linkages, 127 glycans with unique modifications, 46 sphingoids, and 43 fatty acyl groups. It should be helpful for scientists who are interested in GSLs, from isolation and structural analyses to chemical and enzymatic syntheses, as well as their biological studies and applications.

Structural and immunochemical identification of Leb glycolipids in the plasma of a group O Le(a-b-) secretor

Total non-acid glycosphingolipids were isolated from the plasma of a healthy red blood cell group O Le(a-b-) salivary ABH secretor individual. Glycolipids were fractionated by HPLC and combined into eight fractions based on chromatographic and immunoreactive properties. These glycolipid fractions were analysed by thin-layer chromatography and tested for Lewis activity with antibodies reactive to the type 1 precursor (Le(c)), H type 1 (Le(d)), Le(a) and Le(b) epitopes. Fractions were structurally characterized by mass spectrometry (EI-MS and LSIMS) and proton NMR spectroscopy. Expected blood group glycolipids, such as H type 1, (Fuc alpha 1-2Gal beta 1-3GlcNac beta 1-3Gal beta 1-4Glc beta 1-1Cer) were immunochemically and structurally identified. Inconsistent with the red cell phenotype and for the first time, small quantities of Le(b) blood group glycolipids (Fuc alpha 1-2Gal beta 1-3(Fuc alpha 1-4)GlcNAc beta 1-4Glc beta 1-1Cer) were immunochemically and structurally identified in the plasma of a Lewis-negative individual. These findings confirm recent immunological evidence suggesting the production of small amounts of Lewis antigens by Lewis negative individuals.

Isolation and characterization of the major glycosphingolipids from the liver of the rainbow trout (Oncorhynchus mykiss): identification of an abundant source of 9-O-acetyl GD3

The carbohydrate structures of the major glycosphingolipids from the liver of the rainbow trout Oncorhynchus mykiss have been examined. We have isolated and identified four major neutral (glucosylceramide, galactosylceramide, lactosylceramide, and globoside) and five acidic (sulfatide, GM3, GM2, GD1a, and 9-O-Acetyl GD3) glycosphingolipids from trout liver. They have been characterized by 1H nuclear magnetic resonance spectroscopy, methylation analysis, fast atom bombardment mass spectrometry, and specific monoclonal antibodies. Significantly, the relatively scarce ganglioside 9-O-acetyl GD3 was found to comprise approximately 23% of the total ganglioside content of normal rainbow trout liver. 9-O-Acetyl GD3 is, however, abundant in human melanoma and as such, trout liver may be a suitable source of this antigen.

Identification of a blood group A active hexaglycosylceramide with a type 1 carbohydrate chain in plasma of an A1 Le(a-b-) secretor

A blood group A active hexaglycosylceramide with a type 1 carbohydrate chain was identified in the plasma of an A1 Le(a-b-) secretor. The analysis was done on the total non-acid glycosphingolipid fraction using mass spectrometry, NMR spectroscopy, and anti-A antibody immunostaining on thin-layer chromatograms.

1H-n.m.r. analysis of glycolipids possessing mono- and multi-meric X and Y haptens: characterization of two novel extended Y structures from human adenocarcinoma

Analysis of glycolipids having repeating core-structures of type 2 chains ([Gal beta 1----4GlcNAc beta 1----3]nGal beta 1----4Glc beta 1----1Cer) by 1- and 2-dimensional high resolution 1H-n.m.r. spectroscopy shows that fucosylation alpha 1----3 to GlcNAc with or without fucosylation alpha 1----2 to Gal produces predictable chemical shifts of anomeric protons and systematic, glycosylation-induced shift changes. These effects were analyzed for a series of glycolipids of known structure bearing mono- and multimeric X [Gal beta 1----4(Fuc alpha 1----3)GlcNAc beta 1----3] and Y [Fuc alpha 1----2Gal beta 1----4-(Fuc alpha 1----3)GlcNAc beta 1----3] determinants, and were subsequently used to elucidate the primary saccharide structure of two novel glycolipids isolated from human liver adenocarcinoma. They are proposed to be Y determinants carried on a norhexaosylceramide core, with the following structures: (Formula: see text).

Primary structure of a major sialyl-saccharide alditol from human amniotic mucins expressing the tumor-associated sialyl-X antigenic determinant

A major sialyl-saccharide alditol isolated from mucins of human amniotic fluid was purified by high-performance liquid chromatography followed by high-performance thin-layer chromatography of the methylated derivative and subjected to structural analyses which comprised fast atom bombardment and electron impact-mass spectrometry, methylation analysis, exoglycosidase digestion and CrO3 oxidation. The structure of a disialylated pentasaccharide characterized by a sialyl-X antigenic determinant was established: (formula; see text)

Immunochemistry of the Lewis blood-group system: isolation and structures of Lewis-c active and related glycosphingolipids from the plasma of blood-group O Le(a-b-) nonsecretors

Five different glycosphingolipid fractions (GL-3, 285 micrograms; GL-5, 1090 micrograms; GL-6, 615 micrograms; GL-7, 555 micrograms; and GL-8, 155 micrograms) have been isolated from 25 liters of plasma of O Le(a-b-) nonsecretors by means of ethanol extraction, several steps of Folch distribution, and reversed-phase, silicic acid, and ion-exchange column chromatography of native or peracetylated substances. Final purification, accomplished by preparative silica gel high-performance thin-layer chromatography, led to chromatographic homogeneity of GL-3 and GL-6. In the hemagglutination inhibition as well as quantitative passive hemagglutination techniques two of these substances (GL-3, GL-5) exhibited distinct, and the other three (GL-6-GL-8) very strong, Lec blood-group activities when tested against two different Lec antisera of human or goat origin. The fragments' structures were elucidated by fast atom bombardment and electron impact mass spectrometry of permethylated derivatives in order to determine molecular weight, sugar sequence, position of branching points, and type of oligosaccharide chains, as well as fatty acid and sphingosine patterns of the ceramide residue. Combined gas-liquid chromatography and mass spectrometry of partially methylated alditol acetates identified sugar composition and glycosidic linkages. Thus, the following structures could be established: (formula; see text) In contrast to the structurally homogeneous GL-3, minor amounts of 4-O-substituted GlcNAc pointed to a small contamination of GL-6 by branched type 2 ceramide nonasaccharide analogs. Glycolipids containing hepta- or nonasaccharides as in GL-3 or GL-6 could also be identified in fractions GL-5 (ceramide heptasaccharide) and GL-7 and GL-8 (ceramide nonasaccharide). These latter fractions revealed, however, distinct heterogeneity due to the presence of a small amount of either a type 2 analog of GL-3 (GL-5) or linear, mainly type 2, ceramide hexa- (GL-5, GL-7) or octasaccharides (GL-8). In addition to previous immunochemical communications the presented Lec active structures of GL-3 and GL-6 provide evidence that 3-fucosyl-N-acetyllactosamine in combination with a type 1 based oligosaccharide sequence and a 3,6-galactosyl branching point are essential parts of the Lec antigenic determinant (as marked in the formula of GL-6).

Structure of neutral oligosaccharides derived from mucus glycoproteins of human seminal plasma

The primary structures of nine major saccharide alditols in the fraction of neutral carbohydrates derived from human seminal plasma mucin have been established on the basis of fast atom bombardment and electron impact mass spectrometry combined with methylation analysis, exoglycosidase digestion, and CrO3 oxidation, as follows. Formula: see text.

Primary structures and Lewis blood-group-dependent expression of major sialylated saccharides from mucus glycoproteins of human seminal plasma

The primary structures of four major sialylated saccharide alditols derived from mucus glycoproteins of human seminal plasma were established by fast-atom-bombardment mass spectrometry and methylation analysis. Anomeric configurations of the glycosidic bonds were determined by exoglycosidase digestion and CrO3 oxidation. (Formula: see text) Two minor components represent isomers of the major saccharide in A6, which are probably characterized by terminal sequences NeuAc(2----3)Gal(1----4)[Fuc(1----3)]GlcNAc(1---- and Fuc(1----2)Gal(1----4)[NeuAc(2----6)]GlcNAc(1----, respectively. Based on quantitative data from high-pressure liquid chromatography and on structural information, the biosynthetic pathways for neutral and sialylated saccharides related to the Lewis system were proposed. Expression of saccharides A6, A7 and A8 and their asialo counterparts, which are characterized by antigenic determinants H, Lex and Ley, respectively, is qualitatively and quantitatively dependent on the Lewis blood type of the respective donor and correlates with Ca 19-9 activity of its seminal plasma.

Glycosphingolipids of human plasma

A number of glycosphingolipids, including 10 gangliosides, not previously identified in human plasma have been characterized. The plasma contains 2 micrograms of lipid-bound sialic acid/ml plasma and 54% of the gangliosides are monosialo, 30% disialo, 10% trisialo, and 6% tetrasialo. Individual glycosphingolipids were purified by high-performance liquid chromatography and thin-layer chromatography, and were characterized on the basis of their chromatographic mobility, carbohydrate composition, hydrolysis by glycosidases, methylation analysis, and immunostaining with anti-glycosphingolipid antibodies. The monosialogangliosides were identified as GM3, GM2, sialosyl(2-3)- and sialosyl(2-6)lactoneotetraosylceramides, sialosyllacto-N-nor-hexaosylceramide, and sialosyllacto-N-isooctaosylceramide. The major gangliosides in the polysialo fractions contained a ganglio-N-tetraose backbone and were identified as GD3, GD1a, GD1b, and GQ1b. The most abundant neutral glycosphingolipids were glucosyl, lactosyl, globotriaosyl, globotetraosyl and lactoneotetraosylceramides. The other neutral glycosphingolipids, tentatively identified by immunostaining with monoclonal antibodies, contained H1, Lea, Leb, and lacto-N-fucopentose III (X hapten) structures.

Structure of tumor-associated carbohydrate antigen Ca 19-9 on human seminal-plasma glycoproteins from healthy donors

The monoclonal antibody-defined, tumor-associated antigen Ca 19-9, chemically identical with the sialylated Lewisa-carbohydrate determinant of a monoganglioside and a mucin, was demonstrated by radioimmunoassay to be present in large amounts as component of fucose-rich sialoglycoproteins, which had been extracted from human seminal plasma of healthy donors. The carbohydrate antigen of these glycoproteins (m greater than 205 kDa and m 115 kDa), which are presumably secreted by the prostatic gland, was absent in seminal plasma from blood-group-Lewis-negative men. The Ca 19-9 active sialyl-oligosaccharide was cleaved from the proteins by mild alkaline borohydride treatment and was shown to chromatograph on gradient elution from DEAE-Sephadex with the fraction of monosialylated saccharide alditols (MS-SP). The asialo derivative of the major saccharide alditol in this fraction was composed of L-fucose, D-galactose, N-acetyl-D-glucosamine and N-acetyl-D-galactosaminitol in the molar proportions 1:2:1:1 and chromatographed on Bio-Gel P2 according to approximately seven hexose units. A methylation analysis of the sialylated saccharide alditol in fraction MS-SP, which had been purified by high-pressure liquid chromatography, revealed the presence of terminal, non-reducing L-fucose, 3-O-substituted D-galactose, 3,4 di-O-substituted N-acetyl-D-glucosamine and 3-O-substituted N-acetyl-D-galactosaminitol. The presented data and the fragmentation pattern obtained on direct probe EI and FAB+ mass spectrometry of the permethylated asialo derivative are in accordance with the structure of a sialylated pentasaccharide alditol (formula; see text).

Structures of fucose-containing ceramide pentasaccharides from the plasma of blood group O Le(a-b-) nonsecretors

A minor, Lec blood-group inactive ceramide pentasaccharide double band fraction has been isolated from the plasma of blood group O Le(a-b-) nonsecretors. The two purified glycolipids were analysed by NMR spectroscopy, mass spectrometry and combined gas chromatography-mass spectrometry. The following structures could be established: GlcNAc(beta 1----3)Gal(beta 1----4)Glc(beta 1----1)Cer (I); Gal(beta 1----4) [Fuc(alpha 1----3)]GlcNAc(beta 1----3)Gal(beta 1----4)Glc(beta 1----1)Cer (II). It must be concluded that at least part of the secretor gene-independent plasmatic H type 2 blood-group activity can be attributed to glycosphingolipid I, whereas substance II, originally detected in cancerous tissue, also occurs in the plasma of healthy individuals.

Deuterium NMR as a structural probe for micelle-associated carbohydrates: D-mannose

Residual quadrupole splittings for deuterons on perdeuterated alpha- and beta-D-mannose oriented in a potassium laurate liquid crystal have been measured. Multiple quantum two-dimensional NMR spectroscopy at high magnetic field is used to gain sufficient resolution to assign splittings to specific sites within these molecules. The assigned splittings are interpreted in terms of molecular geometries and preferred orientations of the molecules relative to the surface of the potassium laurate micelles that make up the liquid crystalline phase.