Revised structure for the 6-O-methylglucose polysaccharide of Mycobacterium smegmatis

Structural determinants in a glucose-containing lipopolysaccharide from Mycobacterium tuberculosis critical for inducing a subset of protective T cells

Mycobacteria synthesize intracellular, 6-O-methylglucose–containing lipopolysaccharides (mGLPs) proposed to modulate bacterial fatty acid metabolism. Recently, it has been shown that Mycobacterium tuberculosis mGLP specifically induces a specific subset of protective γ₉δ₂ T cells. Mild base treatment, which removes all the base-labile groups, reduces the specific activity of mGLP required for induction of these T cells, suggesting that acylation of the saccharide moieties is required for γ₉δ₂ T-cell activation. On the basis of this premise, we used analytical LC/MS and NMR methods to identify and locate the acyl functions on the mGLP saccharides. We found that mGLP is heterogeneous with respect to acyl functions and contains acetyl, isobutyryl, succinyl, and octanoyl groups and that all acylations in mGLP, except for succinyl and octanoyl residues, reside on the glucosyl residues immediately following the terminal 3-O-methylglucose. Our analyses also indicated that the octanoyl residue resides at position 2 of an internal glucose toward the reducing end. LC/MS analysis of the residual product obtained by digesting the mGLP with pancreatic α-amylase revealed that the product is an oligosaccharide terminated by α-(1→4)–linked 6-O-methyl-d-glucosyl residues. This oligosaccharide retained none of the acyl groups, except for the octanoyl group, and was unable to induce protective γ₉δ₂ T cells. This observation confirmed that mGLP induces γ₉δ₂ T cells and indicated that the acylated glucosyl residues at the nonreducing terminus of mGLP are required for this activity.

Mycobacterium hassiacum recovers from nitrogen starvation with up-regulation of a novel glucosylglycerate hydrolase and depletion of the accumulated glucosylglycerate

Some microorganisms accumulate glucosylglycerate (GG) during growth under nitrogen deprivation. However, the molecular mechanisms underlying the role of GG and the regulation of its levels in the nitrogen stress response are elusive. Since GG is required for biosynthesis of mycobacterial methylglucose lipopolysaccharides (MGLP) we examined the molecular mechanisms linking replenishment of assimilable nitrogen to nitrogen-starved M. hassiacum with depletion of GG accumulated during nitrogen deficiency. To probe the involvement of a newly identified glycoside hydrolase in GG depletion, we produced the mycobacterial enzyme recombinantly and confirmed the specific hydrolysis of GG (GG hydrolase, GgH) in vitro. We have also observed a pronounced up-regulation of GgH mRNA in response to the nitrogen shock, which positively correlates with GG depletion in vivo and growth stimulation, implicating GgH in the recovery process. Since GgH orthologs seem to be absent from most slowly-growing mycobacteria including M. tuberculosis, the disclosure of the GgH function allows reconfiguration of the MGLP pathway in rapidly-growing species and accommodation of this possible regulatory step. This new link between GG metabolism, MGLP biosynthesis and recovery from nitrogen stress furthers our knowledge on the mycobacterial strategies to endure a frequent stress faced in some environments and during long-term infection.

Amphiphilic cytosolic glycans from mycobacteria: occurrence, lipid-binding properties, biosynthesis, and synthesis

Polymethylated polysaccharides (PMPSs), glycans composed of 10-20 carbohydrate residues the majority of which carry a single methyl group, are produced by some mycobacterial species. O-Methylation thus occurs on 20-30% of all the hydroxyl groups within the molecule, rendering them amphiphilic. A property of PMPSs is their ability to form high-affinity complexes with fatty acids and their derivatives, suggesting a role in mycobacterial fatty acid biosynthesis. However, direct evidence for their in vivo function is still lacking. Over the past several decades the lipid-binding properties, biosynthesis, and chemical synthesis of PMPSs have been explored and this review will provide an overview of progress made in these areas.

Diversity, biological roles and biosynthetic pathways for sugar-glycerate containing compatible solutes in bacteria and archaea

A decade ago the compatible solutes mannosylglycerate (MG) and glucosylglycerate (GG) were considered to be rare in nature. Apart from two species of thermophilic bacteria, Thermus thermophilus and Rhodothermus marinus, and a restricted group of hyperthermophilic archaea, the Thermococcales, MG had only been identified in a few red algae. Glucosylglycerate was considered to be even rarer and had only been detected as an insignificant solute in two halophilic microorganisms, a cyanobacterium, as a component of a polysaccharide and of a glycolipid in two actinobacteria. Unlike the hyper/thermophilic MG-accumulating microorganisms, branching close to the root of the Tree of Life, those harbouring GG shared a mesophilic lifestyle. Exceptionally, the thermophilic bacterium Persephonella marina was reported to accumulate GG. However, and especially owing to the identification of the key-genes for MG and GG synthesis and to the escalating numbers of genomes available, a plethora of new organisms with the resources to synthesize these solutes has been recognized. The accumulation of GG as an 'emergency' compatible solute under combined salt stress and nitrogen-deficient conditions now seems to be a disseminated survival strategy from enterobacteria to marine cyanobacteria. In contrast, the thermophilic and extremely radiation-resistant bacterium Rubrobacter xylanophilus is the only actinobacterium known to accumulate MG, and under all growth conditions tested. This review addresses the environmental factors underlying the accumulation of MG, GG and derivatives in bacteria and archaea and their roles during stress adaptation or as precursors for more elaborated macromolecules. The diversity of pathways for MG and GG synthesis as well as those for some of their derivatives is also discussed. The importance of glycerate-derived organic solutes in the microbial world is only now being recognized. Their stress-dependent accumulation and the molecular aspects of their interactions with biomolecules have already fuelled several emerging applications in biotechnology and biomedicine.

Chapter 2: Biogenesis of the cell wall and other glycoconjugates of Mycobacterium tuberculosis

The re-emergence of tuberculosis in its present-day manifestations - single, multiple and extensive drug-resistant forms and as HIV-TB coinfections - has resulted in renewed research on fundamental questions such as the nature of the organism itself, Mycobacterium tuberculosis, the molecular basis of its pathogenesis, definition of the immunological response in animal models and humans, and development of new intervention strategies such as vaccines and drugs. Foremost among these developments has been the precise chemical definition of the complex and distinctive cell wall of M. tuberculosis, elucidation of the relevant pathways and underlying genetics responsible for the synthesis of the hallmark moieties of the tubercle bacillus such as the mycolic acid-arabinogalactan-peptidoglycan complex, the phthiocerol- and trehalose-containing effector lipids, the phosphatidylinositol-containing mannosides, lipomannosides and lipoarabinomannosides, major immunomodulators, and others. In this review, the laboratory personnel who have been the focal point of some to these developments review recent progress towards a comprehensive understanding of the basic physiology and functions of the cell wall of M. tuberculosis.

Initiation of methylglucose lipopolysaccharide biosynthesis in mycobacteria

Background

Mycobacteria produce two unique families of cytoplasmic polymethylated polysaccharides - the methylglucose lipopolysaccharides (MGLPs) and the methylmannose polysaccharides (MMPs) - the physiological functions of which are still poorly defined. Towards defining the roles of these polysaccharides in mycobacterial physiology, we generated knock-out mutations of genes in their putative biosynthetic pathways.

Methodology/Principal Findings

We report here on the characterization of the Rv1208 protein of Mycobacterium tuberculosis and its ortholog in Mycobacterium smegmatis (MSMEG_5084) as the enzymes responsible for the transfer of the first glucose residue of MGLPs. Disruption of MSMEG_5084 in M. smegmatis resulted in a dramatic decrease in MGLP synthesis directly attributable to the almost complete abolition of glucosyl-3-phosphoglycerate synthase activity in this strain. Synthesis of MGLPs in the mutant was restored upon complementation with wild-type copies of the Rv1208 gene from M. tuberculosis or MSMEG_5084 from M. smegmatis.

Conclusions/Significance

This is the first evidence linking Rv1208 to MGLP biosynthesis. Thus, the first step in the initiation of MGLP biosynthesis in mycobacteria has been defined, and subsequent steps can be inferred.

Complexation of fatty acids and fatty acid-CoAs with synthetic O-methylated polysaccharides

An experimentally simple, but highly reproducible and reliable method has been developed to follow the complexation event of fatty acid (FA) and FA-CoA with polysaccharides. This method was based on the recent discovery of the unique blue-shifted UV absorption associated with the aggregation of tetraenoic fatty acids (TE-FAs) in aqueous solution. Complexation was monitored by recording the intensity of UV absorption at 250 nm ([free TE-FA]) and 303 nm ([complexed TE-FA]), and the K aggregate of C(20) t,t,t,t-TE-FA exhibited the ideal property for this purpose. Synthetic 3-O-methyl-D-mannose- and 6-O-methyl-D-glucose-containing lipopolysaccharides were found to exhibit a broad range of the binding affinities with C(20) t,t,t,t-TE-FAs as well as saturated FAs/FA-CoAs.

Genetic basis for the biosynthesis of methylglucose lipopolysaccharides in Mycobacterium tuberculosis

Mycobacteria produce two unusual polymethylated polysaccharides, the 6-O-methylglucosyl-containing lipopolysaccharides (MGLP) and the 3-O-methylmannose polysaccharides, which have been shown to regulate fatty acid biosynthesis in vitro. A cluster of genes dedicated to the synthesis of MGLP was identified in Mycobacterium tuberculosis and Mycobacterium smegmatis. Overexpression of the putative glycosyltransferase gene Rv3032 in M. smegmatis greatly stimulated MGLP production, whereas the targeted disruption of Rv3032 in M. tuberculosis and that of the putative methyltransferase gene MSMEG2349 in M. smegmatis resulted in a dramatic reduction in the amounts of MGLP synthesized and in the accumulation of precursors of these molecules. Disruption of Rv3032 also led to a significant decrease in the glycogen content of the tubercle bacillus, indicating that the product of this gene is likely to be involved in the elongation of more than one alpha-(1-->4)-glucan in this bacterium. Results thus suggest that Rv3032 encodes the alpha-(1-->4)-glucosyltransferase responsible for the elongation of MGLP, whereas MSMEG2349 encodes the O-methyltransferase required for the 6-O-methylation of these compounds.

Bacterial capsular antigens. Structural patterns of capsular antigens

Structural patterns of bacterial capsular antigens including capsular polysaccharides and exoglycans are given in this review. In addition, the immunological activity of capsular antigens and their role in type specificity of bacteria are discussed.

Newly found 2-N-acetyl-2,6-dideoxy-beta-glucopyranose containing methyl glucose polysaccharides in M.bovis BCG: revised structure of the mycobacterial methyl glucose lipopolysaccharides

The specific mycobacterial methyl polysaccharides 3- O -methyl mannose polysaccharide (MMP) and the 6- O -methyl glucose lipopolysaccharides (MGLPs) were shown to modulate the fatty acid biosynthesis by the mycobacterial fatty acid synthetase I (FAS I). This activity is attributed to their fatty acid complexing properties allowing the release of the neo synthesized fatty acyl chain from the enzyme and probably their transport in the cell. To elucidate, at a molecular level, the mechanism of this unusual kind of polysaccharide-lipid biological interaction, we first analyzed, by mass spectrometry and proton nuclear magnetic resonance (1H NMR) spectroscopy, the structure of the polysaccharidic backbone (MGPs) of the MGLPs from Mycobacterium bovis BCG. This work reveals that this strain produces a new kind of MGP containing an unusual monosaccharide never described in the mycobacterial genus: a 2- N -acetyl-2,6-dideoxy-beta-glucopyranosyl. In addition,1H NMR data afforded evidence for the revision of three glycosidic linkages described previously. These modifications affect mainly the reducing end tetrasaccharide and have great consequences on the previously proposed molecular model of the MGP.

Direct evidence of methylglucose lipopolysaccharides/palmitoyl-CoA noncovalent complexes by capillary zone electrophoresis-electrospray/mass spectrometry

Mycobacterial methylglucose lipopolysaccharides (MGLPs) play an important regulatory role in the biosynthesis of long-chain fatty acids by forming complexes with neosynthesized acyl-CoA fatty acid derivatives. The MGLPs from Mycobacterium smegmatis were purified by high-performance anion-exchange chromatography and characterized by LSIMS and CE/ESI-MS. We investigated their interaction with palmitoyl-CoA using capillary zone electrophoresis with both direct and indirect UV detection. In the latter mode, the signal of the UV-transparent MGLPs decreased upon addition of increasing amounts of palmitoyl-CoA; while using direct UV detection, the addition of palmitoyl-CoA to the MGLPs revealed characteristic profiles. The major peak was assigned to the noncovalent MGLP/palmitoyl-CoA complex on the basis of its electrophoretic mobility. The abundance of the complex was found to increase until the MGLP/palmitoyl-CoA molar ratio reached a 1/1 stoichiometry. The existence of and the stoichiometry of this complex were assessed by CE/ESI mass spectrum analysis, showing pseudomolecular ions of the MGLP/palmitoyl-CoA complex. These results confirm that CE/ESI-MS is a powerful tool to characterize noncovalent molecular association.

Structural elucidation of novel methylglucose-containing polysaccharides from Mycobacterium xenopi

The structures of methylglucose-containing polysaccharides (MeGlc PS) from Mycobacterium xenopi were investigated using high-pH anion-exchange chromatography and liquid secondary-ion mass spectrometry. We report the structure of two novel MeGlc PS, referred to as A and B. MeGlc PS A is composed of 16 D-glucopyranose residues, 11 of which are methylated, and MeGlc PS B contains 15 D-glucopyranose residues, 10 of which are methylated. The main structural feature of both MeGlc PS A and B, compared to the previously described structures, is the absence of the tetrasaccharide non-reducing end 3-O-Me-D-Glcp-[alpha(1-->4)-D-Glcp]3. The MeGlc PS A structure is similar to the synthetic polysaccharide [Saïer, M. H. & Ballou, C. E. (1968) J. Biol. Chem. 243, 992-1005], having a lower affinity for fatty acids than the MeGlc PS of Mycobacterium smegmatis [Kiho, T. & Ballou, C. E. (1988) Biochemistry 27, 5824-5828]. Thus, the occurrence of MeGlc PS A and the consequences on the regulation of fatty acid synthetase I activity involved in the biosynthesis of fatty acids, precursors of mycolic acid biosynthesis, is discussed.

Polysaccharides from Peptostreptococcus anaerobius and structure of the species-specific antigen

The cell-envelope antigens of Peptostreptococcus anaerobius were extracted from intact cells by autoclave or alkaline treatment. The purified species-specific antigen (G) was identified among several polysaccharides obtained from the extracts by successive treatments with ribonuclease and pronase followed by ion-exchange and gel-filtration chromatography. G was investigated by 13C- and 31P-n.m.r. spectroscopy, titrimetry, elemental analysis, and gas-liquid chromatography. Oxidation of G with NaIO4 followed by reduction with NaBH4 and mild acid hydrolysis yielded the Smith degradation product of G (GS). Treatment of G and GS with 48% HF gave the respective dephosphorylated products GF and GSF. The structures of GS, GF, and GSF were investigated by 13C-n.m.r. spectroscopy, methylation analysis, and gas-liquid chromatography-mass spectrometry. The principal constituents of G were 2-acetamido-2-deoxy-D-glucose (D-GlcNAc), D-glyceric acid, and phosphate as a diester, in the ratio 2:1:1, and a minor amount of D-glucose (beta-D-Glcp). GS contained D-GlcNAc, D-glyceric acid, glycerol, and phosphate in a 1:1:1:1 ratio. GF and GSF contained D-GlcNAc and D-glyceric acid in the ratios 2:1 and 1:1, respectively. A structure for the principal repeating unit of polymeric G compatible with the analytical data consists of alpha-D-GlcpNAc-(1----3)-alpha-D-GlcpNAc-(1----2)-D-glyceric acid units linked through C-6'-C-6" phosphate diester bridges. This structure is novel for two reasons: (a) unsubstituted glyceric acid residues occur as aglycons in the repeating structure, and (b) phosphate diester bridges link nonanomeric glycose carbons in a non-nucleic acid polymer. The structural role of the minor amount of beta-D-Glcp in G remains unknown.

Thermodynamic parameters and shape of the mycobacterial polymethylpolysaccharide-fatty acid complex

Properties of the mycobacterial polymethylpolysaccharide-lipid complex have been investigated by fluorometric techniques. From the dissociation constant for the O-methyglucose polysaccharide-parinaric acid complex at 293 K, a Gibbs free energy (delta G degree) of -33.65 kJ/mol was obtained. The Kd decreased with increasing temperature, giving an enthalpy (delta H degree) of 15.4 kJ/mol. From these data, a molar entropy (delta S degree) of 167.4 J K-1 was obtained. Thus, the reaction is slightly endothermic, but the large positive entropy change leads to an overall negative free energy favoring complex formation. From fluorescence depolarization measurements, the methylglucose polysaccharide-parinaric acid complex appears to display isotropic rotation with a correlation time of 2.55 ns at 23 degrees C. This may be compared to a rotational correlation time of 6.17 ps for free parinaric acid in water at 23 degrees C calculated from the value determined in cyclohexanol at the same temperature, which demonstrates that the mobility of the fatty acid in the complex is restricted. Assuming the complex is spherical, it was calculated to have a diameter of 23-26 A, whereas a helical methyglucose polysaccharide molecule assembled from space-filling models has the dimensions of a cylinder of 18 X 24 A. The polysaccharide and fatty acid chain-length dependence of the interaction shows a discontinuity for helical polysaccharide segments shorter than 12 sugars and for fatty acids shorter than palmitate.

Order of enzymic incorporation of O-methyl groups into the O-methyl-D-glucose-containing polysaccharide of Mycobacterium smegmatis. A tritium-labelling study

The order of enzymic incorporation of O-methyl groups into the O-methyl-D-glucose-containing polysaccharide (MGP) of Mycobacterium smegmatis, 3MG(J)----G(I)----G(H) ----G(G)----6MG(F)----(GMG)9(E)----[G(L)----G(D)]----G(C) ----[G(K)----G(B)]----G(A)----Ga, where G is D-glucose, 3MG is 3-O-methyl-D-glucose, 6MG is 6-O-methyl-D-glucose, and Ga is D-glyceric acid, was studied by incubating cultures of M. smegmatis with L-[3H-Me]methionine for various times. MGP was then extracted from the cells, and relative radioactivities of residues D, (E + F)average and J, or of D, E average, F, and J, were determined. Tritium-labelling of these residues increased in the reducing-to-nonreducing residue direction, the steepness of the gradient becoming more shallow with increasing incubation time. The results are consistent with a biosynthetic mechanism that involves sequential addition of O-methyl groups to residues of the pre-formed D-glucan, in the reducing-to-nonreducing residue direction.

Continuous-flow fast atom bombardment-mass spectrometry of permethylated oligosaccharides: a comparative study of direct mixture analysis with packed capillary column liquid chromatography-fast atom bombardment-mass spectrometry

Conventional positive fast atom bombardment (FAB) and continuous-flow FAB analysis were carried out with permethylated lacto-N-tetraose. This latter method, a new approach, has been used to analyze a mixture of permethylated oligosaccharides by liquid chromatography-mass spectrometry (LC-MS) with a packed capillary fused-silica column and the continuous-flow probe as interface. Under these conditions, we found the continuous-flow probe to be superior to the conventional probe because its low matrix level increased the signal-to-noise ratio. The analysis of the mixture of permethylated oligosaccharide alditols obtained from hen ovomucoid by LC-MS using the continuous-flow probe as interface is described.

Synthesis of 6-deoxymaltooligosaccharides and a study of their lipid-binding properties

Amylose reacted in N,N-dimethylformamide with crystalline bromomethylenedimethylammonium bromide (Vilsmeier bromide) to give 6-bromo-6-deoxyamylose with a high degree of substitution. Reduction of the bromoamylose with sodium borohydride yielded 6-deoxyamylose that, following controlled acetolysis, gave 6-deoxymaltooligosaccharides. Such oligosaccharides, of appropriate chain-length, formed stable complexes with long-chain fatty acids that have a dissociation constant of about 2 microM in their interaction with parinaric acid (trans-9,11,13,15-octadecatetraenoic acid). Treatment of 6-bromoamylose with sodium methoxide in dimethyl sulfoxide produced a 3,6-anhydroamylose that contains few unaltered D-glucose units. This anhydroamylose also bound to a palmitoyl-resin column, suggesting that the polymer may be partially helical and somewhat lipophylic. Finally, reaction of 6-bromoamylose with methylvinyl ether led to the 2,3-di(methoxyethyl) ether that, on reaction with sodium methoxide, gave the 6-methyl ether from which 6-O-methylamylose was obtained by mild acid hydrolysis.

Complete 1H-n.m.r. assignments for two core-region oligosaccharides of human meconium glycoproteins, using 1D and 2D methods at 500 MHz

The complete 1H-n.m.r. assignments for alpha-D-GalNAc-(1----3)-D-GalNAc-ol and beta-D-Gal-(1----4)-beta-D-GlcNAc-(1----6)-D-GalNAc-ol have been made using a combination of 2D correlation experiments (COSY, RELAYED-COSY, and F1-decoupled) and an analysis of the high-resolution 1D-n.m.r. spectra at 500 MHz.

Enzymic degradation of the mycobacterial O-methyl-D-glucose polysaccharide by a Rhizopus-mold alpha amylase, an enzyme active on 6-O-methyl-amylo-oligosaccharides

An enzyme activity that catalyzes hydrolysis of an alpha-(1----4)-linked 6-O-methyl-D-glucan was detected in, and purified from, Rhizopus oryzae mold. The enzyme acts like an alpha amylase and digests unmodified amylo-oligosaccharides 10 to 15 times as fast as it does the 6-O-methyl and 6-deoxy derivatives. When the limit product obtained by digesting the mycobacterial O-methyl-D-glucose polysaccharide with pancreatic alpha amylase and Aspergillus glucoamylase was further digested with the Rhizopus alpha amylase, di-, tri-, and tetra-saccharide fragments composed of alpha-(1----4)-linked 6-O-methyl-D-glucose were released. The rest of the molecule was recovered as oligosaccharides terminated by two, or three, alpha-(1----4)-linked 6-O-methyl-D-glucose residues.

Laser desorption Fourier transform mass spectra of malto-oligosaccharides

Laser desorption mass spectra of malto-oligomers, including starch, have been obtained using Fourier transform mass spectrometry. Fragmentations of these oligomers have been examined after doping with metal salts to obtain cation-attachment ions. Doping starch with NaCl, KBr and Ag2O results in analogous cation-attachment oligosaccharide fragment ions for all three metal ions. A distinct and unusual fragmentation pattern is observed for the larger oligomers.

Enhancement of structural information in FAB ionized carbohydrate samples by neutral gas collision

Fast atom bombardment (FAB) ionization and two coupled analyzers (BE-EB) have been combined with neutral gas collision (C) to enhance structural information in the mass spectra of oligosaccharides. (B and E are abbreviations for magnetic and electric sectors respectively.) FAB ionization and the first analysers (BE) have provided parent ions free from biological and liquid matrix contaminants. Structural detail of these products were observed after collision and daughter ion analysis in a second coupled analyser (EB). Starting from complex mixtures, this instrumental approach, BE-C-EB, has provided specific oligomeric sequence information which was not observed in the normal FAB mass spectra. Collision spectra obtained from isomeric linear and branched oligosaccharides show unique fragments that can be directly related to structure.

Trehalose-containing lipooligosaccharides from mycobacteria: structures of the oligosaccharide segments and recognition of a unique N-acylkanosamine-containing epitope

The structures of the oligosaccharide segments of nine trehalose-containing lipooligosaccharides (LOS) of Mycobacterium kansasii have been established by positive and negative fast-atom bombardment mass spectrometry, acetolysis, partial acid hydrolysis, methylation analyses, and nuclear magnetic resonance. Upon acetolysis, all produce the alpha,alpha-trehalose-containing tetraglucose (Glc4) "core" -beta-D-Glcp(1----3)-beta-D-Glcp(1----4)-alpha-D-Glcp(1----1)-alpha-D-Gl cp. The simplest (LOS I') contains an additional alpha 1----3-linked 3-O-methyl-L-rhamnopyranose (3-O-Me-L-Rhap) unit; those of intermediate complexity (LOS I-III) contain an additional D-xylopyranose (D-Xylp) residue or xylobiose in beta 1----4 linkage; and those of ultimate complexity (LOS IV-VIII) contain further D-Xylp residues and the distal N-acylkanosamine- (KanNAcyl) and fucopyranosyl- (Fucp) containing disaccharide KanNAcyl(1----3)Fucp. Thus, the structure of the oligosaccharide from LOS VII is KanNAcyl(1----3)Fucp(1----4) [-beta-D-Xylp(1----4)]6-alpha-L-3-O-Me-Rhap(1----3)Glc4++ +. Polyclonal rabbit and murine monoclonal antibodies react only with the more complex KanNAcyl-Fucp-containing lipooligosaccharides, indicating that the KanNAcyl distal end, not the trehalose end, contains the antibody binding site unique to M. kansasii and is responsible for the serological distinctiveness of M. kansasii among mycobacterial species.

Structural analysis of the O-glycosidically linked core-region oligosaccharides of human meconium glycoproteins which express oncofoetal antigens

Glycoproteins were extracted from meconium samples of group O neonates of secretor type by pronase digestion followed by precipitation in 67% aqueous ethanol and separated into Ii antigen enriched and depleted fractions by affinity chromatography. The latter fraction strongly expressed the oncofoetal antigens recognised by natural antibodies in mouse sera and the hybridoma antibody FC 10.2, and this activity was enhanced after mild acid hydrolysis to remove sialic acid and fucose residues. Oligosaccharides were released from the mild-acid-treated fraction by base-borohydride degradation and purified by gel permeation chromatography on Bio-Gel P4 and high performance liquid chromatography on octadecylsilyl and aminopropylsilyl columns. The major oligosaccharides were characterised by fast atom bombardment and electron impact mass spectrometry, combined gas-liquid chromatography/mass spectrometry and 500-MHz proton NMR spectroscopy. Their structures, in order of abundance, were: (Formula: see text).

Fast atom bombardment mass spectrometry of glycosphingolipids. Glycosphingolipids containing neutral sugars

Natural and synthetic glycosphingolipids containing neutral sugars have been analyzed by positive and negative ion fast atom bombardment mass spectrometry. Basic structural characterization including saccharide size and sequence and ceramide composition is possible on the basis of the fragment ions observed. The degree of fragmentation could be increased by using higher sample concentrations and lower fast atom beam energies. Commercially available synthetic compounds that had been presumed to be pure were shown to contain homologous fatty acids. Mixtures of glycosphingolipids such as those obtained from Gaucher's spleen and from human erythrocytes can be characterized and quantitated.

Structural characterization of oligosaccharides by high-performance liquid chromatography, fast-atom bombardment-mass spectrometry, and exoglycosidase digestion

A method for structural characterization of oligosaccharides after preparing uv-absorbing derivatives is described. The derivatives can be rapidly analyzed and purified by high-performance liquid chromatography, with separation of various structures determined primarily by size and sugar composition. Derivatization requires as little as 0.5-1.0 nmol of oligosaccharide, and detection of down to 50 pmol of oligosaccharide is possible by monitoring absorbance at 229 nm. In addition, the carbohydrate portion of the derivative was found to retain its sensitivity to exoglycosidases, allowing sequential enzymatic digestions for determination of sugar sequence and anomerity to be performed. The derivatives also possessed a site of potential positive charge, making them amenable to analysis by fast-atom bombardment-mass spectrometry. Permethylation of the derivatives permitted their separation by capillary gas chromatography, thus allowing investigation of their structures by gas chromatography-mass spectrometry. The combination of these techniques will allow almost the complete structure of small amounts of oligosaccharides to be determined.