Structural determination of D-mannans of pathogenic yeasts Candida stellatoidea type I strains: TIMM 0310 and ATCC 11006 compared to IFO 1397

Structural characterization and evaluation of prebiotic activity of oil palm kernel cake mannanoligosaccharides

In this study, mannanoligosaccharides (MOS) were isolated from palm kernel cake by aqueous extraction using high temperature and pressure. Structural characterization of MOS was carried out using acid hydrolysis, methylation analysis, ESI-MS/MS and 1D/2D NMR. The prebiotic activity of MOS was evaluated in vitro using two probiotic Lactobacillus strains. Sugar analysis indicated the presence of mannose in each of the oligomers. Methylation and 1D/2D NMR analysis indicated that the MOS have a linear structure consisting of (1→4)-β-d-mannopyranosyl residues. ESI-MS/MS results showed that the isolated mannan oligomers, MOS-III, MOS-IV, MOS-V and MOS-VI consist of tetra-, penta-, hexa-, and hepta-saccharides with molecular weights of 689, 851, 1013 and 1151Da, respectively. Based on the in vitro growth study, MOS-III and MOS-IV was found to be effective in selectively promoting the growth of Lactobacillus reuteri C1 strain as evidenced by the optical density of the culture broth.

Concise assembly of linear alpha(1-->6)-linked octamannan fluorescent probe

Synthesis of a fluorescently labelled (dansylated) linear alpha(1-->6)-linked octamannan, using glycosyl fluoride donors and thioglycosyl acceptors is described. A selective and convergent two-stage activation progression was executed to construct di-, tetra and octa-mannosyl thioglycosides in three glycosylation steps with excellent yield. Further a 5-N,N-Dimethylaminonaphthalene-1-sulfonamidoethyl (dansyl) group was coupled to 1-azidoethyl octamannosyl thioglycoside. Global deprotection of the coupled product afforded the desired dansylated homo-linear alpha(1-->6)-linked octamannan.

Synthesis of a heptasaccharide fragment of the mannan from Candida guilliermondii cell wall and its conjugate with BSA

The 3-aminopropyl glycoside of a heptasaccharide fragment of the cell wall mannan from Candida guilliermondii 18, which corresponds to the antigenic Factor 9, has been synthesized by a convergent approach based on glycosylation of a tetrasaccharide acceptor with a trisaccharide donor as the key step to give a protected heptasaccharide 17. Subsequent two-step deprotection of 17 afforded the heptamannoside 18, which was then conjugated with BSA using the squarate procedure.

Influence of outer region mannosylphosphorylation on N-glycan formation by Candida albicans: normal acid-stable N-glycan formation requires acid-labile mannosylphosphate addition

The pathogenic yeast Candida albicans produces large N-glycans with outer regions containing only mannose residues. The outer region comprises a primary branch with multiple secondary and tertiary branches. Tertiary branches are linked to secondary branches by phosphodiester bridges. In the current model of outer chain elongation in the genetically related yeast Saccharomyces cerevisiae, synthesis of the branches occurs sequentially, primary to tertiary. Thus, disruption of mannosylphosphorylation, the initial step in tertiary branch formation, should not affect primary or secondary branch production. Compared to its wild-type parent, a C. albicans mutant defective in tertiary branch mannosylphosphorylation (mnn4Delta/mnn4Delta) made outer regions with reduced susceptibility to low acid acetolysis treatment, suggesting that the secondary or primary region had been modified. Higher acid acetolysis conditions were required to release the secondary branches from the primary branches. The released secondary branches constitute the subset of the wild-type secondary branches that lack a phosphate group. In contrast, the acid-stable region of both wild-type and mnn4Delta S. cerevisiae strains required high acid acetolysis conditions to release the secondary branches, despite having smaller and less complex secondary and tertiary branches. These results suggest that the complex and longer secondary and tertiary branches of C. albicans affect the conformation of the acid-stable region to render it more susceptible to acetolysis which implies secondary and tertiary branch formation in C. albicans are interdependent events and occur concurrently, rather than sequentially.

Synthesis of Escherichia coli O9a polysaccharide requires the participation of two domains of WbdA, a mannosyltransferase encoded within the wb* gene cluster

WbdA (previously MtfA) is one of the mannosyltransferases encoded within the Escherichia coli O9a wb* gene cluster. It is composed of two domains of similar size, connected by an alpha-helix chain. Elimination of the C-terminal half by transposon insertion or gene deletion caused synthesis of an altered structural O-polysaccharide consisting only of alpha-1,2-linked mannose. O9a polysaccharide synthesis was restored by the C-terminal half of WbdA in trans. No membrane incorporation of mannose from GDP mannose was observed in a strain carrying only the gene for truncated WbdA. For mannose incorporation, it was necessary to introduce both wbdB and wbdC genes into the strain. Therefore, it is likely that the N-terminal half of truncated WbdA synthesizes the altered O-polysaccharide together with other mannosyltransferases which participate in the initial reactions of the O9a polysaccharide synthesis. Both N- and C-terminal domains of WbdA are required for the synthesis of the complete E. coli O9a polysaccharide. The chi sequence location between the two domains and homology plot analyses of the wbdA and the WbdA protein suggested that the wbdA gene might have arisen by fusion of two independent genes.

Demonstration of the presence of alpha-1,6-branched side chains in the mannan of Candida stellatoidea

A mild acetolysis of the mannans of Candida stellatoidea was performed after acetylation to yielded an alpha-1,6-branched mannohexaose, the presence of which had been predicted from the appearance of a specific H1-H2-correlated cross-peak in two-dimensional homonuclear Hartmann-Hahn spectroscopy. In this study, we found that the de-O-acetylation of a 4-O-acetyl group at the branching point, the 3,6-di-O-substituted mannose unit, of an acetylated oligosaccharide by sodium methoxide is significantly slower than that of other acetyl groups. We could separate the 4-O-acetylated branching oligosaccharide from linear isomer using high-performance liquid chromatography. Before and after the de-O-acetylation of the purified branching oligosaccharide, their 1H-NMR signals were sequentially assigned by means of the nuclear Overhauser effect. In the sequential NMR assignment study, we showed that the alpha-1,6-linked mannose unit is attached to the 3-O-substituted unit based on the presence of NOE cross-peak between H1 of the branching mannose unit and H6 of the 3-O-substituted mannose unit. An enzyme-linked immunosorbent inhibition assay of the reactivity of factor 4 serum to C. stellatoidea mannan by several oligosaccharides indicated that the alpha-1,6-branched oligosaccharide and the beta-1,2 linkage-containing oligosaccharides showed inhibitory activity. This result indicates that factor 4 serum, as well as factor 5 and 6 sera, contains antibodies against beta-1,2-linked mannose units which have been reported to participate in pathogenicity via cytokine production and/or adherence. From the assignment results of H1-H2-correlated cross-peaks of oligosaccharides and mannans, the molar ratio of the mannan side chains was proposed. In this study, we demonstrated that the epitope structure of the C. stellatoidea type I strains was the same as that of the C. albicans NIH B-792 (serotype B) strain.

Identification of the antigenic determinants of factors 8, 9, and 34 of genus Candida

We investigated the antigenic determinants of factors 8, 9, and 34 of the genus Candida among pathogenic yeasts by enzyme-linked immunosorbent assay (ELISA) using mannans of Saccharomyces cerevisiae wild type and mutant types, mnn 1-mnn 4 and mnn 2. Results of ELISA including antisera against the antigenic factors of genus Candida (Candida Check, latron; FAbs) indicated that these three types of mannan distinctly react with FAbs 34, 8 and 9, respectively. To identify the recognition sites of these FAbs, we compared the ability of various oligosaccharides to inhibit the binding of the mannans to FAbs. The results indicated that FAb 34 preferentially recognizes linear side chains containing a non-reducing terminal alpha-1,3-linked mannose residue, Man(alpha)1 --> 3Man(alpha)1 --> (2Man(alpha)1 --> )n(2Man) (n > or = 0), and that one of the recognition sites of FAb 9 is linear alpha-1,6-linked oligomannosyl series, Man(alpha)1 --> (6Man(alpha)1 --> )n(6Man) (n > or = 2). On the other hand, the recognition site of FAb 8 apparently consisted of two alpha-1,2-linked oligomannosyl side chains and an alpha-1,6-linked mannose residue that originated from the mannan backbone, Man(alpha)1 --> 2Man(alpha)1 --> 2(Man(alpha)1 -->2Man(alpha)1 --> 6)Man.

Antigenicity of cell wall mannans of Candida albicans NIH B-792 (serotype B) strain cells cultured at high temperature in yeast extract-containing sabouraud liquid medium

Cultivation of Candida albicans NIH B-792 (serotype B) at high temperature (37 degrees C) for 48 h in yeast extract-containing Sabouraud liquid medium (YSLM) provided the following findings in comparison with the findings obtained after incubation at 27 degrees C. Growth of the blastoconidia of this strain was decreased, with a dry weight of 9%, and the cells were deficient in cytokinesis. The cells did not undergo agglutination with serum factor 5 from a commercially available serum factor kit (Candida Check). Mannan (B-37-M) obtained from the cells cultured at 37 degrees C had partially lost its reactivity against serum factor 4 and lost most of its reactivity against serum factor 5 in an enzyme-linked immunosorbent assay (ELISA) in contrast to that (B-27-M) at 27 degrees C. Both cells and mannan prepared by cultivation first at 37 degrees C and then at 27 degrees C entirely recovered their reactivities with serum factors 4 and 5. 1H-nuclear magnetic resonance analysis also revealed that B-37-M had lost a beta-1,2-linked mannopyranose unit and retained a phosphate group. Similar changes were observed in the three other serotype B strains used in the study. The beta-1,2-linked mannooligosaccharides longer than mannotetraose were not included among the products released from B-37-M by mild acid treatment. The results of the inhibition ELISA with a series of beta-1,2-linked mannooligosaccharides from biose to octaose (M2 to M8, respectively) showed that the reactivity against serum factor 4 was inhibited most strongly by the oligosaccharides M4 to M8 and that the reactivity against serum factor 5 was inhibited completely by relatively longer oligosaccharides, M5 to M8, indicating their participation as the antigenic factor 5 epitopes.

Detection of beta-1,2-mannosyltransferase in Candida albicans cells

A particulate insoluble fraction from Candida albicans J-1012 (serotype A) strain cells was obtained as the residue after extracting a 105,000 x g pellet of cell homogenate with 1% Triton X-100. Incubation of this fraction with a mannopentaose, Man beta 1-->2Man alpha 1-->(2Man alpha 1-->)(2)2Man (alpha beta Man5), in the presence of GDP-mannose followed by high performance liquid chromatography showed the formation of a mannohexaose. Analysis of the product by 1H NMR indicates that alpha beta Man5 was changed to Man beta 1-->2Man beta 1-->2Man alpha 1-->(2Man alpha 1-->)2 2Man (alpha beta Man6). This beta-1,2-mannosyltransferase (ManTase) II activity was completely inhibited by Zn2+ and was not restored by the addition of EDTA. The corresponding enzyme fraction from C. albicans NIH B-792 (serotype B) strain cells, the mannan of which does not possess both the alpha beta Man5 and alpha beta Man6 side chains, also exhibited the same beta-1,2-ManTase II activity.

Structural modification of cell wall mannans of Candida albicans serotype A strains grown in yeast extract-Sabouraud liquid medium under acidic conditions

The cell wall mannans of two Candida albicans serotype A strains, NIH A-207 and J-1012 (abbreviated as A and J strains, respectively), cultured in yeast extract-Sabouraud liquid medium at pH 2.0, contained neither a phosphate group nor a beta-1,2-linked mannopyranose unit (H. Kobayashi, P. Giummelly, S. Takahashi, M. Ishida, J. Sato, M. Takaku, Y. Nishidate, N. Shibata, Y. Okawa, and S. Suzuki, Biochem. Biophys. Res. Commun. 175:1003-1009, 1991). In this study, the mannans obtained from A and J strains grown in pH 2.0 medium (abbreviated as mannans A2 and J2, respectively) exhibited quite different reactivities against rabbit anti-C. albicans and anti-Saccharomyces cerevisiae sera compared with those of mannans from the corresponding strains cultured in conventional medium at pH 5.9 (abbreviated as mannans A and J, respectively). Namely, mannans A2 and J2 lost reactivity against the former serum but reacted with the latter serum to a higher extent than mannans A and J. In order to account for these difference in more detail, mannans A2 and J2 were subjected to acetolysis. Elution profiles of the acetolysates were completely different from those of acetolysates obtained from mannans A and J reported in our previous papers. The 1H nuclear magnetic resonance spectra of the oligosaccharides from mannans A2 and J2 obtained by this procedure indicate that the side chains are composed of alpha-linked mannopyranose units densely linked to the alpha-1,6-linked backbone. The long side chains containing one alpha-1,3-linked mannopyranose unit are markedly increased.

Structures of cell wall mannans of pathogenic Candida tropicalis IFO 0199 and IFO 1647 yeast strains

We conducted a structural analysis of the cell wall mannans isolated from two Candida tropicalis strains, IFO 0199 and IFO 1647, exhibiting strong agglutinabilities against anti-Candida factor sera 5 and 6. The products released from these mannans by acid treatment were identified as the oligosaccharides, from biose to pentaose, consisting solely of beta-1,2-linked mannopyranose units corresponding to common epitopes of Candida albicans serotypes A and B (factor 5). Mild acetolysis of acid- and alkali-treated mannans produced large amounts of hexaose and heptaose, Man rho beta 1-2Man rho beta 1-2Man rho alpha 1-2Man rho alpha 1-2Man rho alpha 1-2Man and Man rho beta 1-2Man rho beta 1-2Man rho beta 1-2Man rho alpha 1-2 Man rho alpha 1-2Man, corresponding to the C. albicans serotype A-specific epitopes (factor 6). However, the homologous pentaose, Man rho beta 1-2Man rho alpha 1-2 Man, was not generated by this procedure. The oligosaccharides (biose to hexaose) obtained from the mannans by conventional acetolysis were composed exclusively of alpha-1,2-linked mannopyranose units. Therefore, the mannans of C. tropicalis IFO 0199 and IFO 1647 do not have the alpha-1,3-linked mannopyranose units previously observed in the mannans of C. albicans and Candida stellatoidea. The results of this study and previous findings indicate that the similarity of the antigenicities of three Candida species, C. albicans serotype A, C. stellatoidea type II, and C. tropicalis, reside in the beta-1,2 and alpha-1,2 linkages containing oligomannosyl side chain (factor 6) in the cell wall mannan.

Isolation and preliminary characterization of the 14- to 18-kilodalton Candida albicans antigen as a phospholipomannan containing beta-1,2-linked oligomannosides

Western blot (immunoblot) analysis of Candida albicans germ tube extracts has demonstrated the probable presence of beta-1,2-linked oligomannosides acting as epitopes distributed over a 14- to 18-kDa antigen unreactive to concanavalin A. These conclusions about the existence of these non-mannan-associated oligomannoside species were reinforced in the present study by the demonstration of reactivity of factor serum 5 (Iatron Laboratories) with the same antigen. A monoclonal antibody which reacted in an enzyme immunoassay with beta-1,2-linked oligomannosides converted into neoglycolipids and in Western blotting with the 14- to 18-kDa antigen from yeast and germ tubes, through metaperiodate-sensitive epitopes, was used for further characterization of the molecule. Reducing agents and strong protease digestion, which have deleterious effects on C. albicans proteins and mannoproteins, affected neither the antigenicity nor the relative molecular weight of the molecule. Western blots performed after migration of protease-treated extracts in polyacrylamide gels without sodium dodecyl sulfate (SDS) showed that the 14- to 18-kDa antigen could be negatively charged, whereas metabolic radiolabeling demonstrated that these charges could originate, at least in part, from the presence of phosphorus within the molecule. Chloroform-methanol-water extraction of protease-resistant material led to purification of the 14- to 18-kDa antigen, as determined by SDS-polyacrylamide gel electrophoresis and Western blotting. Metabolic radiolabeling with mannose confirmed the presence of these sugar residues within the purified 14- to 18-kDa antigen (despite its nonreactivity to concanavalin A), whereas radiolabeling with palmitic acid demonstrated its lipopolysaccharidic nature. Together, these results led to the conclusion that the 14- to 18-kDa antigen is a phospholipomannan.

Structure of the D-mannan of the pathogenic yeast, Candida stellatoidea ATCC 20408 (type II) strain, in comparison with that of C. stellatoidea ATCC 36232 (type I) strain

Acid treatment of the cell-wall D-mannas of Candida stellatoidea strains ATCC 36232 (Type I, A3 strain) and ATCC 20408 (Type II, A2 strain) gave (1----2)-linked beta-D-manno-oligosaccharides (dp 2-5), whereas treatment with alkali gave the (1----2)-linked alpha-D-mannobiose. Conventional acetolysis of the acid- and alkali-treated D-mannan of the A3 strain gave oligosaccharides consisting of (1----2)- and (1----3)-linked alpha-D-mannopyranose residues, similar to those of Candida albicans serotype B strain. Mild acetolysis of the acid- and alkali-treated D-mannan of the A2 strain gave higher oligosaccharides that were digested by the Arthrobacter GJM-1 strain exo-alpha-D-mannosidase. The results of 1H- and 13C-NMR analyses indicated this D-mannan to contain branches with the following structures: beta-D-Manp-(1----2)-alpha-D-Manp-(1----2)-alpha-D-Manp++ +-(1----2)-alpha-D-Manp- (1----2)-D-Man, beta-D-Manp-(1----2)-beta-D-Manp-(1----2)-alpha-D-Manp -(1----2)- alpha-D-Manp-(1----2)-D-Man, and beta-D-Manp-(1----2)-beta-D-Manp-(1----2)-beta- D-Manp-(1----2)-alpha-D-Manp-(1----2)-alpha-D-Manp-(1- ---2)-alpha-D-Manp- (1----2)-D-Man, in common with the D-mannans of C. albicans serotype A strains.

Evidence for oligomannosyl residues containing both beta-1,2 and alpha-1,2 linkages as a serotype A-specific epitope(s) in mannans of Candida albicans

In order to identify the branches containing both beta-1,2 and alpha-1,2 linkages as the serotype A-specific epitope(s) in the mannans of Candida albicans, serotype A strains with oligosaccharides constituting the beta-1,2 linkage, the alpha-1,2 linkage, and both the beta-1,2 and the alpha-1,2 linkages were prepared from the mannans of C. albicans serotype A strains (NIH A-207 and J-1012) and tested for their inhibitory effects in the precipitin and slide agglutination assays. The results indicated that two oligosaccharides containing both beta-1,2 and alpha-1,2 linkages, Manp beta 1-2Manp alpha 1-2Manp alpha 1-2Manp alpha 1-2Man and Manp beta 1-2Manp beta 1-2Manp alpha 1-2Manp alpha 1-2Manp alpha 1-2Man, served as epitopes participating in the serotype A specificity of C. albicans strains.

Structural study of a cell wall mannan-protein complex of the pathogenic yeast Candida glabrata IFO 0622 strain

We conducted a structural analysis of the cell wall mannan-protein complex (mannan) isolated from a pathogenic yeast, Candida glabrata IFO 0622 strain. The chemical structure of mannobiose released from this mannan by treatment with 10 mM HCl at 100 degrees C for 1 h was identified as Manp beta 1-2Man. The treatment of this mannan with 100 mM NaOH at 25 degrees C for 18 h gave a mixture of alpha-1,2- and alpha-1,3-linked oligosaccharides, from tetraose to biose, and mannose. The acid- and alkali-stable mannan moiety was subjected to mild acetolysis with a 100:100:1 (v/v) mixture of (CH3CO)2O, CH3COOH, and H2SO4 at 40 degrees C for 36 h. The resultant three novel oligosaccharides, tetraose, hexaose, and heptaose, were identified as Manp beta 1-2Manp alpha 1-2Manp alpha 1-2Man, Manp alpha 1-2Manp alpha 1-2Manp alpha 1-6Manp alpha 1-2Manp alpha 1-2Man, and Manp alpha 1-3Manp alpha 1-2Manp alpha 1-2Manp alpha 1-6Manp alpha 1- 2Manp alpha 1-2Man, respectively, in addition to the three known oligosaccharides, Manp alpha 1-2Man, Manp alpha 1-2Manp alpha 1-2Man, and Manp alpha 1-3Manp alpha 1-2Manp alpha 1-2Man. A sequential analytical procedure involving partial acid hydrolysis with hot 0.3 M H2SO4, methylation, fast atom bombardment mass, and 1H NMR analyses was quite effective in the structural determination of the novel oligosaccharides. The results indicate that this mannan possesses a structure closely resembling that of Saccharomyces cerevisiae X2180-1A wild type strain, with the presence of small amounts of oligomannosyl residue, Manp beta 1-2Manp alpha 1-X, corresponding to one of the epitopes dominating serotype-A specificity of Candida spp., in addition to branches corresponding to hexaose and heptaose each containing one intermediary alpha-1,6 linkage.