Carbon-13 nuclear-magnetic-resonance spectroscopy of Forssman hapten

The 13C n.m.r. spectrum of Forssman hapten was obtained at 25.16 MHz in [3H] chloroform/[2H] methanol (1:1, v/v), using purified glycosphinogolipid from canine intestinal mucosa (glycolipid I). All amide, olefin, anomeric, intersaccharide glycosidic ether, amide linkage, methyl and many methylene resonances were resolved and assigned. Analysis of the anomeric region reveals the following pentaglycosylceramide structure as originally proposed [Siddiqui & Hakomori (1971) J. Biol. Chem. 246, 5766-5769]: GalNAc (alpha 1 leads to 3) GalNAc (beta 1 leads to 3) Gal (alpha 1 leads to 4) Gal (beta 1 leads to 1) ceramide. Analysis of the amide, olefin and methylene regions reveals no alpha-hydroxy fatty acyl group and less than or equal to 6 mol% unsaturated fatty acyl groups are present. Chemical-shift assignments are reported for the anomeric and glycosidic ether carbon atoms of intersaccharide-linked alpha-galactose and N-acetyl-alpha-galactosamine residues. Two rules are proposed for the assignment of the anomeric form of 1 leads to 3 and 1 leads to 4 linkages of galactose and N-acetylgalactosamine residues present in the glycone of glyco-conjugates. The present study emphasizes the importance of the anomeric "window" (80-120 p.p.m.) in studies of glycone structure.

Isolation and characterization of a novel monosialosylpentahexosyl ceramide from Tay-Sachs brain

A novel monosialoganglioside was isolated from Tay-Sachs brains. It represented about 0.1% of the total ganglioside mixture. Compositional analysis by gas-liquid chromatography indicated that it contained glucose, galactose, N-acetylgalactosamine, N-acetylneuraminic acid, and long chain base in the molar ratio of 1:2:2:1:1. The ganglioside was found to be resistant to neuraminidase (Clostridium perfringens), beta-hexosaminidase (jack bean), and beta-galactosidase. However, it could be degraded by a human liver beta-hexosaminidase preparation in the presence of an activator to produce a glycolipid chromatographically identical with authentic IV3NeuAc-GgOse4-ceramide. This glycolipid product was resistant to beta-galactosidase (jack bean), but could be readily degraded to GgOse4-ceramide by neuraminidase. Mild formic acid hydrolysis degraded the intact ganglioside to an asialo derivative chromatographically identical with the pentahexosyl ceramide (GalNAc-Gal-GalNAc-Gal-Glc-ceramide) derived from GD1a-GalNAc. The asialo derivative could then be degraded to GgOse4-ceramide and GgOse3-ceramide by sequential treatment with jack bean beta-hexosaminidase and beta-galactosidase. These data suggest that the novel ganglioside is a monosialosylpentahexosyl ceramide with the sialosyl group attached to the penultimate galactose moiety of the pentahexosyl ceramide backbone, and it has the following structure: GalNAc(beta 1-4)Gal(beta 1-3)GalNAc(beta 1-4)Gal(beta 1-4)Glc-ceramide (formula see text).

Isolation and characterization of an endo-beta-galactosidase from a new strain of Escherichia freundii

A new strain of Escherichia freundii was isolated from human feces. Compared with the previous strain (Kitamikado, M., and Ueno, R. (1970) Bull. Jpn. Soc. Sci. Fish. 36, 1175-1180), this strain releases comparable levels of endo-beta-galactosidase with lower levels of exoglycosidases in the culture medium containing 0.3% of keratan sulfate. Endo-beta-galactosidase was purified by an improved purification procedure involving Amicon H1P10 hollow fiber filtration, QAE-Sephadex A-50, and CM-Sephadex C-50 chromatographies. The purified enzyme is completely free from proteases and exoglycosidases. The general properties of this enzyme are: molecular weight, 28,000; optimal pH, 5.5 TO 5.8; PI, pH 8.0. This enzyme hydrolyzed keratan sulfates isolated from different sources to produce 6-O-sulfo-GlcNAc beta1 leads to 3Gal as the major product. In addition, the specificity of this enzyme toward various glycoconjugates was also studied.

Evidence for the presence of two separate protein activators for the enzymic hydrolysis of GM1 and GM2 gangliosides

Two different protein activators were isolated simultaneously from human liver for the enzymic hydrolysis of GM1 (Gal beta 1 leads to 3GalNAc beta 1 leads to 4Gal(3 comes from 2 alpha NeuAc)beta 1 leads to 4Glc-Cer) by beta-galactosidase and GM2 (GalNAc beta 1 leads to 4Gal(3 comes from 2 alpha NeuAc)beta 1 leads to 4Glc-Cer) by beta-hexosaminidase A. The hydrolysis of GM1 is stimulated only by the GM1-specific activator which has very little effect on the hydrolysis of GM2. The same is also true for the hydrolysis of GM2. The antiserum raised against GM1 activator did not cross-react with GM2 activator and vice versa. These results suggest the presence of two different activators for the separate hydrolysis of GM1 and GM2. In connection with the enzymic hydrolysis of GM1 and GM2, we found that the hydrolysis of GM2 by human hepatic beta-N-acetylhexosaminidase A was severely inhibited by a buffer of high ionic strength, whereas no such inhibition was observed in the hydrolysis of GM1 by beta-galactosidase.

Effect of endo-beta-galactosidase on intact human erythrocytes

Endo-beta-galactosidase, a glycosidase that hydrolyzes Gal beta 1-4 GlcNAc linkages in glycoconjugates, has been used to probe the plasma membrane of human erythrocytes. Coomassie blue staining of stroma components separated by sodium dodecyl sulfate-acrylamide gel electrophoresis indicates that treatment of red cells with endo-beta-galactosidase converts Protein 3, the anion transporter of the erythrocyte, to a more compact staining band. No other components detected by Coomassie staining are affected. Following labeling of red cells with galactose oxidase + NaB3H4, 45 to 50% of the [3H]galactose residues can be released by endo-beta-galactosidase. In contrast, only 5% of the label incorporated by treatment with periodate + NaB3H4, can be removed. [3H]Galactose residues are released from three components: Protein 3, Band 4.5, and the megaloglycolipids. The susceptibility of these components to endo-beta-galactosidase, together with the high content of Gal and GlcNAc present in Protein 3 and the megaloglycolipids, suggests that the erythrocyte membrane contains several components with N-acetyllactosamine repeating units, a structure commonly found in connective tissue glycoconjugates.

Isolation and characterization of a heptaglycosylceramide from bovine erythrocyte membranes

A heptaglycosylceramide was isolated from bovine erythrocyte membranes. The structure was characterized to be Gal(alpha 1-3)Gal(beta 1-4)GlcNAc(beta1-3)Gal(beta 1-4)Glc-NAc(beta 1-4)al(beta 1-4)GlcCer. A hexaglycosylceramide that has the same sequence except for the terminal alpha-galactosyl unit has also been isolated. We have previously found that gangliosides isolated from bovine erythrocyte membranes contain a keratan sulfate type repeating unit --[3Gal(beta 1-4)-GlcNAc beta]--n. This study shows that the keratan sulfate type repeating unit is also present in the neutral glycosphingolipids of bovine erythrocyte membranes.

Carbon 13 NMR spectroscopy of a cerebroside. Proof of the beta-pyranosyl structure of D-glucosylceramide

The first 13C nuclear magnetic resonance spectrum of a cerebroside is reported. All signals of D-glucosylceramide (I), the cerebroside from human Gaucher's diseased liver, have been assigned by comparison of their chemical shifts with those of model compounds. This data has been used to demonstrate for the first time directly: (a) that the glucosyl moiety must exist in the pyranoside ring form and have a beta anomeric linkage, and (b) that the fatty acyl composition of the aglycon is: alpha-hydroxy, 0%; saturated, 86 +/- 2%; unsaturated long chain, 14 +/- 2%; and unsaturated short chain, less than or equal to 2%. The use of 13C signal shifts in the delta 80 to 120 region (anomeric window) for the assignment of glycon anomeric and ring forms demonstrated herein should be applicable to other glycoconjugates.

Erythroglycan, a high molecular weight glycopeptide with the repeating structure [galactosyl-(1 leads to 4)-2-deoxy-2-acetamido-glucosyl(1 leads to 3)] comprising more than one-third of the protein-bound carbohydrate of human erythrocyte stroma

Glycopeptides of molecualr weight range 7,000 to 11,000, unusual in size and structure, have been partially purified from pronase digests of lipid-free human erythrocyte ghosts; we term this fraction "erythroglycan." These substances comprise about one-third of the galactose and glucosamine of the ghost. Methylation analysis of erythroglycan yields mainly 4-linked glucosamine, 3-linked galactose, and 3,6-linked galactose, along with mannose and fucose derivatives. Hydrazinolysis and nitrous acid deamination degrade erythroglycan to galactosyl-2,5-anhydromannose, indicating a repeating structure of galactosyl, (1 leads to 4)-2deoxy-2-acetamidoglucosyl (1 leads to 3). Digestion with the endo-beta-galactosidase from Escherichia freundii gives only partial cleavage of the erythroglycan, probably because of the arborized structure indicated by the branched galactose. Since sphingosine is not detectable after methanolysis by chemical ionization mass spectrometry, and since amino acids are present, we conclude that these substances are probably glycopeptidic in origin and are not "macroglycolipids." Erythroglycan may have the same type of keratan-like core structure as the long chain blood group glycolipids from human erythrocytes and could be a protein-bound carrier of the ABO determinants.

Occurrence of glycosphingolipids in chicken egg yolk

Chicken egg yolk was found to contain a unique glycosphingolipid pattern not seen in other types of tissue or cell. These glycosphingolipids were isolated in pure form and their structures established by sequential enzymic hydrolysis and permethylation analysis. The major gangliosides in chicken egg yolk are N-acetylneuraminosylgalactosylceramide, N-acetylneuraminosyl-lactosylceramide and di-N-acetylneuraminosyl-lactosylceramide. The only neutral glycosphingolipid found in chicken egg yolk is galactosylceramide.

Increased glycosphingolipid excretion associated with proteinuria

The urine of patients with proteinuria of various etiologies was examined to determine if proteinuria alone was associated with significant glycosphingolipiduria. In all cases of proteinuria examined, the level of glycosphingolipids in the urine was found to be markedly elevated. There was no evidence of a glycosphingolipid storage disorder in any case. It was concluded that significant glycosphingolipiduria may occur in proteinuria as well as in the glycosphingolipid storage disorders.

Characterization of gangliosides from bovine erythrocyte membranes

Two glucosamine-containing gangliosides, sialosylhexaglycosylceramides, were isolated from bovine erythrocyte membranes. Both gangliosides were hydrolyzed by neuraminidase isolated from Clostridium perfringens to become neutral hexaglycosylceramides. Based on the results of sequential enzymatic hydrolysis and gas chromatography-mass spectrometric analyses of the methylated sugars, the structures of these two gangliosides were shown to be NeuAcalpha2 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4Glc-ceramide and NeuGcalpha2 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4Glc-ceramide, respectively. In addition, N-acetyl- and N-glycolylneuraminosyllacto-N-neotetraosylceramides, and N-acetyl- and N-glycolylneuraminosyllactosylceramides were also found in bovine erythrocytes. The predominant fatty acids in these two gangliosides were C 22:0 and C 24:0. C-18 sphingosine was the major base detected.

Characterization of dog small intestinal fucolipids with human blood group A activity. Differences in dog and human A-active fucolipids

Glycolipids containing fucose (fucolipids) which carried human blood group A activity were isolated from a number of dog small intestines and analyzed. On the basis of sugar analysis, methylation, periodate oxidation, enzyme degradation, mass spectrometry, and immunologic studies, a structure is proposed for these substances. The ceramides of the dog fucolipids containing only hydroxylated fatty acids with 85% saturated and 15% monoenoic acids ranging from 16 to 25 carbon atoms. Sphingosine and phytosphingosine comprised 48% each of the long chain bases. An A-active fraction isolated from human small intestine was shown to have two components, one of which was immunologically distinct and the other identical with the dog intestinal fucolipids. The human fraction differed from the dog fucolipids in migration on thin-layer chromatography and contained two types of amino sugar substitution. It is proposed that the human fraction was composed of two fucolipids with incomplete structures.

Cell wall studies of Histoplasma capsulatum and Blastomyces dermatitidis using autologous and heterologous enzymes

Enzymes capable of hydrolyzing cell walls of Blastomyces dermatitidis and chemotypes I and II of Histoplasma capsulatum were prepared in the laboratory or obtained from commercial sources. They included chitinases, beta-1,3-glucanases, beta-1,6-glucanase, and Pronase. Monosaccharides and disaccharides of glucose released from the cell walls by the enzymes were determined qualitatively by paper and gas-liquid chromatography, and monosaccharides were quantitated by the latter technique as well. An enzyme system isolated from Streptomyces sp. containing both chitinase and glucanase released maximum amounts of glucose and N-acetylglucosamine from the cell walls of H. capsulatum chemotype I. A chitinase preparation, free of glucanase, from Serratia marcescens released only chitobiose and N-acetylglucosamine from chemotype I cell walls, but the total quantity of N-acetylglucosamine released was about 60% less than that released by the Streptomyces system. A beta-1,3-glucanase from Bacillus circulans hydrolyzed the cell walls of H. capsulatum chemotype I, but a beta-1,6-glucanase failed to release glucose from the same walls. Autolytic enzymes, viz., beta-1,3-glucanases and several glycosidases were detected as constitutive enzymes in both yeast and mycelial phases of B. dermatitidis and H. capsulatum chemotypes I and II. No difference in the amount of activity was found between cell sap and culture filtrate preparations. The beta-glucanases prepared from the Histoplasma and Blastomyces strains were active on the cell walls of the yeast phases of H. capsulatum chemotypes I and II, releasing laminaribiose and glucose, but were essentially inactive on the cell walls of B. dermatitidis. Chitinase, beta-1,6-glucanase, alpha-glucanase, and alpha-glucosidase activities were absent from these fungal enzyme preparations.

beta-Mannosidase from the mushroom Polyporus sulfureus

beta-D-Mannosidase (EC 3.2.1.25), a useful tool for the structural studies of heterosaccharide chains, has been isolated in a highly purified form from the fruiting bodies of the mushroom Polyporus sulfureus. This mushroom is unique among reported sources of this enzyme in that it has the advantage of being almost free of alpha-mannosidase activity. The purification procedure involves ammonium sulfate fractionation followed by Sephadex G-100 filtration and chromatography on columns of DEAE-cellulose and hydroxylapatite. The final enzyme preparation gives essentially a single band on disc gel electrophoresis. The purified enzyme liberates the beta-D-mannopyranosyl unit from various natural substrates such as the core glycopeptide, Man(GlcNAc)2-Asn isolated from ovalbumin, from Taka-amylase A, and from human alpha1-acid glycoprotein. It also hydrolyzes (Man)2-GlcNAc from the urine of an alpha-mannosidosis patient, 1,4-D-mannobiose and mannotriose isolated from ivory nut mannan, 4-O-beta-D-mannopyranosyl-L-rhamnose, 6-O-beta-D-mannopyranosyl-D-galactose and 4-O-beta-D-mannopyranosyl-N-acetylglucosamine. The molecular weight of this enzyme is estimated to be about 64,000 by gel filtration. For p-nitrophenyl-beta-D-mannopyranoside, the pH optimum is between 2.4 and 3.4 and the Km is 1.6 mM.

An activator stimulating the enzymic hydrolysis of sphingoglycolipids

An activator stimulating the enzymic hydrolysis of sphingoglycolipids has been purified from human liver. The purity of the activator, as examined by disc gel electrophoresis, showed one major band stained with both amido black and periodate-Schiff reagent. Chemical analyses identify the activator as a glycoprotein. The physical properties of the activator are: heat-stable, nondialyzable; molecular weight, about 21,000; isoelectric point (pI), 4.1. The purified activator stimulates the hydrolysis of GM1 by beta-galactosidase, GM2 by beta-hexosaminidase, as well as ceramide trihexoside by alpha-galactosidase A or B. The hydrolysis by glycosidases depends upon the amount of activator added. An antibody against the activator was developed from rabbits. The specificity of the antibody to the activator has been established. The antibody was used to make the affinity column for isolation of the activator. It was also used to develop a sensitive immunodiffusion method to detect the activator.

Isolation and characterization of jack bean beta-galactosidase

A simple procedure has been devised to isolate beta-galactosidase from jack bean meal. The final preparation gives one major protein banc in disc gel electrophoresis. The substrate specificity of this enzyme toward some natural oligosaccharides, glycoproteins, and sphingoglycolipids has been examined in detail. Among three isomers of N-acetyllactosamine, Galbeta1leads to4GlcNAc; while Galbeta1leads to3GlcNAc was hydrolyzed very slowly. This property can be used to distinguish the galactose linkage in asialo-GM1 (Galbeta1leads to3GalNAcbeta1leads to4Galbeta1leads to4Glcleads toCer) and that in lacto-N-neotetraosylceramide (Galbeta1leads to4GlcNAcbeta1leads to 3Galbeta1leads to4Glcleads toCer). For hydrolyzing glycolipids, the effect of sodium taurodeoxycholate and sodium taurochenodeoxycholate on the rate of hydrolysis was carefully examined. This enzyme hydrolyzes lactosylceramide and asialo-GM1 faster than GM1. These results suggest that in addition to the type and linkage of the penultimate sugar unit, the sugar unit at the distal position of the saccharide chain also affects the hydrolysis rate. It also readily liberates 80% D-galactosyl units from asialo alpha1-acid glycoprotein. Escherichia coli beta-galactosidase on the other hand cannot hydrolyze asialo-alpha1-acid glycoprotein, lactosylceramide, GM1, asialo-GM1, and lacto-N-neotetraosylceramide. The molecular weight of this enzyme is about 75,000 and the isoelectric point is pH 8.0. With p-nitrophenyl beta-D-galactopyranoside as substrate, optimal activity occurs at pH 2.8 with glycine-HCl buffer and at pH 3.5 with citrate-phosphate buffer. With lactose as substrate, the pH optimum in these two buffers are 2.8 and 4.0, respectively. Km values for p-nitrophenyl beta-D-galactopyranoside, o-nitrophenyl beta-D-galactopyranoside and lactose are 0.51 mM, 0.63 mM, and 12.23 mM, respectively. Many inhibitors for this enzyme including inorganic ions, monosaccharides, and glycosides are investigated. In contrast to E. coli beta-galactosidase, jack bean beta-galactosidase is not inhibited by p-aminophenyl thio-beta-D-galactopyranoside.

Characterization of human alpha-galactosidase A and B before and after neuraminidase treatment

It has been previously reported that following neuraminidase treatment alpha-galactosidase A is converted into the B form, as revealed by electrophoresis. By a variety of techniques such as isoelectrofocusing, DEAE-chromatography and by enzyme kinetic parameters, no conversion of alpha-galactosidase A into B, or the reverse, could be detected after neuraminidase treatment. Only an apparent transformation of alpha-galactosidase A into B was revealed by Cellogel electrophoresis. In addition, a discrepancy was noticed between the pattern of electrophoretic migration on starch gel and Cellogel and the net electrical charges of the two alpha-galactosidases as deduced by isoelectrofocusing and DEAE-cellulose. Neuraminidase treatment did not affect the activity of alpha-galactosidase A towards the natural substrate, ceramidetrihexoside, but the activity of alpha-galactosidase B decreased by about 30% under the same conditions. The two forms of alpha-galactosidases A and B used in this study were extensively purified by classical procedures.

Structures of ceramide tetrasaccharides from various sources: uniqueness of rat kidney ceramide tetrasaccharide

Methylation analysis of ceramide tetrasaccharide isolated from human erythrocytes gave acetates of 2,3,6-tri-O-methylgalactitol and 2,4,6-tri-O-methylgalactitol in a ratio of 1:1, and about 50% of the galactose was oxidized by periodate. Rat kidney ceramide tetrasaccharide gave, in contrast, a much larger proportion of the acetates of 2,4,6-tri-O-methylgalactitol (ratio 1:0.3), and less than 20% of the galactose was oxidized by periodate. Sequential degradation by beta-N-acetylhexosaminidase, alpha-galactosidase, and beta-galactosidase showed ceramide tetrasaccharides to have identical carbohydrate sequences and anomeric structures. The major part of ceramide trihexoside derived from rat kidney ceramide tetrasaccharide migrated on thin-layer chromatography more slowly than that derived from other ceramide tetrasaccharides. The structure of a major part of rat kidney ceramide tetrasaccharide was thus determined to be GalNAcbeta(1-->3)Galalpha(1-->3)Galbeta(1-->4)Glcbeta(1-->1)Cer, whereas other ceramide tetrasaccharides have Galalpha(1-->4) structure at the penultimate residue.

On the structure of cytolipin R, a ceramide tetrahexoside hapten from rat lymphosarcoma

Cytolipin R, a ceramide tetrahexoside isolated from rat lymphosarcoma, was studied by sequential hydrolysis with specific glycosidases which revealed the anomeric configurations of the glycosidic bonds. Sugar linkages were established by combined gas-liquid chromatography and mass spectrometry of the partially methylated alditol acetates prepared after permethylation and hydrolysis of the intact lipid. Results indicated the structure of cytolipin R to be N-acetylgalactosaminyl(beta1-->3)galactosyl(alpha1-->3) galactosyl(beta1-->4)glucosyl ceramide. Cytolipin K (globoside I) differs in having a -galactosyl(alpha1-->4)galactosyl- internal linkage, and this difference must account for the immunological differences between cytolipin K and cytolipin R.