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PubMed2004

Analysis of the oligosaccharide chain of human serum immunoglobulin g in patients with localized or metastatic cancer.

A quantitative imbalance between matrix metalloproteinases produced by cancer cells and tissue inhibitors of metalloproteinases produced by fibroblasts and other types of cells has been demonstrated to be a causative factor in invasion and metastasis of cancer cells. On the other hand, it is reported that sugar chains of adhesion molecules such as integrins and CD44 also influence the metastasis of cancer cells. Here, alterations of serum IgG oligosaccharide chain structure were investigated during tumor progression using the new method of fluorophore-assisted carbohydrate electrophoresis (FACE). The structure of serum IgG oligosaccharide chains from 22 cancer patients (11 localized cancer, 11 metastatic cancer) and 10 healthy controls was evaluated by FACE. It was clearly demonstrated that serum IgG oligosaccharide chains without galactose (agalactosyl IgG oligosaccharide) significantly increased with tumor progression of lung and gastric cancers. It is concluded that a marked increase of agalactosyl IgG oligosaccharide in these cancer patients is associated with carcinogenesis and metastasis. Therefore, the analysis of serum IgG oligosaccharide chain structure by FACE may be useful for evaluating diagnosis and prognosis in patients with these carcinomas.

Aged↗
PubMed1982

Utilization of intravenously administered glucose-oligosaccharides in growing miniature pigs.

The ability of intravenously administered glucose or glucose oligosaccharides to supply 12% of the energy requirement of the growing miniature pig was determined. All pigs were fed a stock diet from days 5-28 of life, and a central venous catheter was inserted at 29 days. For the next 30 days, all pigs were fed both enterally and parenterally. Positive control pigs were fed the stock diet with infusions of an isotonic balanced electrolyte solution. Negative control and test animals were fed a diet containing cellulose to replace 12% of energy. Negative control animals received the balanced electrolyte solution intravenously, while test animals received either intravenous glucose of glucose oligosaccharides at levels providing 12% of energy. Carbohydrate utilization was measured by urinary loss of carbohydrate, as well as by growth and body composition. Chemical analyses of the urine indicated utilization of both glucose and glucose oligosaccharides. Glucose oligosaccharides were utilized less well (85%) than glucose (greater than or equal to 99%). No statistically significant differences in weight gain were noted between groups, although weight gain in negative control animals and those animals infused with glucose oligosaccharide solutions were lower than those in the other groups. Body fat analyses also indicated that glucose oligosaccharide solutions were less effective than glucose as an energy source.

Animals↗
PubMed1994

Glycosylation of thyroglobulin secreted by porcine cells cultured in chamber system: thyrotropin controls the number of oligosaccharides and their anionic residues.

Porcine thyroid cells were cultured in porous bottom chambers in the presence or in the absence of TSH added to the basal medium. Radiolabeled-sugar (3H-mannose) was added to the basal medium on day 11 for 4 days and the glycosylation of thyroglobulin (Tg), the major glycoprotein secreted into the apical medium, was studied. The incorporation of 3H-mannose per molecule of Tg was increased 1.5-fold by a 50 microU/ml minimal concentration of TSH. The distribution of glycopeptides (after pronase digestion) on concanavalin A sepharose column was not modified by the presence of TSH. However this distribution was different from that observed for Tg extracted from gland (more multiantennary units than biantennary units and polymannose units). After desialylation and desulfation, the sizes of the oligosaccharide chains analyzed on HPLC appeared similar when cells were cultured under stimulation or not. Thus TSH enhanced sugar incorporation without modifying either the distribution of the different oligosaccharide moieties or their sizes. Consequently the effect of TSH was a 1.5-fold increase in oligosaccharide chains linked to asparagine residues. 3H-Mannose-oligosaccharide chains were then analyzed on ion-exchange HPLC before and after desialylation and desulfation. The number of anionic residues per oligosaccharide unit (particularly sulfate residues) was higher in the absence of TSH than in the presence of TSH. Nevertheless, since TSH increased the number of carbohydrate units per molecule of Tg 1.5-fold, the total content of anionic residues bound to oligosaccharide units per molecule of Tg seems not to be modified by TSH.

Animals↗
PubMed1988

Relationship of oligosaccharide modification to the cause of serum thyroxine-binding globulin excess.

T4-binding globulin (TBG), a glycoprotein with four N-glycosyl complex oligosaccharide chains, exhibits sialic acid-dependent microheterogeneity on isoelectric focusing (IEF). Increasing the sialic acid content of TBG increases its anodal IEF mobility and decreases its rate of in vivo degradation, a mechanism for the elevation of serum TBG levels in pregnancy. In this study, the structure of oligosaccharides in TBG from subjects with various conditions associated with TBG excess was determined by measuring the proportion that bound to Concanavalin-A (Con-A). Since oligosaccharides with three or more branches (antennae) attached to the trimannosyl core are excluded from binding to Con-A, the percentage of serum TBG not bound to Con-A (% peak A) represented the portion of TBG molecules with three or more antennae in all oligosaccharide chains interacting with Con-A. Peak A contained the most anodal IEF bands, while the Con-A-bound TBG (peak B) contained the cathodal bands. Serum samples from 10 normal men and 10 premenopausal women did not significantly differ in terms of TBG levels, % peak A, or IEF mobility and were combined as a single group (normal). Eight subjects with elevated serum TBG levels due to inherited TBG excess [62.0 +/- 10.1 (+/- SD) mg/L] or 2 receiving 5-fluorouracil treatment (26.2 and 31.3 mg/L) compared to 20 normal (14.7 +/- 3.3 mg/L) had % peak A values and IEF mobility similar to those in normal subjects. On the other hand, high serum TBG levels in 8 women during the third trimester of pregnancy (39.2 +/- 5.3 mg/L), 2 women taking oral contraceptives (25.7 and 27.0 mg/L), and 3 women with acute hepatitis (34.8 +/- 4.8 mg/L) were associated with significant elevations of % peak A values (5.68 +/- 1.73%, 3.31% and 2.41%, and 3.25 +/- 0.78%, respectively) compared to those in normal subjects (1.33 +/- 0.40%), as well as increased anodal mobility on IEF. Treatment of a man for 3 days with ethinyl estradiol produced similar changes. Using data from densitometry measurements of IEF bands of TBG, the degree of anodal shift was quantitated (anodal index). This index correlated with the % peak A (r = 0.92) in all study subjects. We conclude that increased sites for sialylation, resulting from the increased proportions of triantennary oligosaccharide chains, account for the increased anodal mobility of TBG in hyperestrogenemia and hepatitis. Thus, in these two conditions, a reduced TBG degradation rate resulting from oligosaccharide modification is the likely mechanism of increased serum TBG levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed2002

Effect of chitosan oligosaccharide on 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced oxidative stress in mice.

The abilities of two types of chitosan oligosaccharides, chitosan oligosaccharide I (1-kDa<MW<3-kDa) and chitosan oligosaccharide II (3-kDa<MW<5-kDa), to prevent 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced oxidative stress were examined in ICR mice. Chitosan oligosaccharide I had no effect on TCDD-induced alterations in lipid peroxidation and glutathione S-transferase activity or liver weight change. However, mice treated with chitosan oligosaccharide II were protected from TCDD-induced lipid peroxidation, inhibition of glutathione peroxidase and glutathione S-transferase activities, and losses in body and liver weights. These results suggest that chitosan oligosaccharide might be a potential agent for combating TCDD-induced pathogenesis.

Animals↗
PubMed2006

Enzymatic synthesis of oligosaccharides and neoglycoconjugates.

Oligosaccharides involved in glycoconjugates play important roles in a number of biological events. To elucidate the biological functions of oligosaccharides, sufficient quantities of structurally defined oligosaccharides, are of limited availability by traditional purification methods, are required. Hence, chemical and enzymatic syntheses of oligosaccharides are becoming increasingly important in glycobiology and glycotechnology. In addition, oligosaccharides often occur as glycoconjugates attached to proteins or lipids. Hence, the development of simple and effective methods for synthesizing neoglycoconjugates such as neoglycoprotein and neoglycolipids is essential for an understanding of the biological function of these molecules. Here we review the most recent developments in the enzymatic synthesis of oligosaccharides and neoglycoconjugates.

Animals↗
PubMed1984

Inhibitors of the biosynthesis and processing of N-linked oligosaccharides.

A number of glycoproteins have oligosaccharides linked to protein in a GlcNAc----asparagine bond. These oligosaccharides may be either of the complex, the high-mannose or the hybrid structure. Each type of oligosaccharides is initially biosynthesized via lipid-linked oligosaccharides to form a Glc3Man9GlcNAc2-pyrophosphoryl-dolichol and transfer of this oligosaccharide to protein. The oligosaccharide portion is then processed, first of all by removal of all three glucose residues to give a Man9GlcNAc2-protein. This structure may be the immediate precursor to the high-mannose structure or it may be further processed by the removal of a number of mannose residues. Initially four alpha 1,2-linked mannoses are removed to give a Man5 - GlcNAc2 -protein which is then lengthened by the addition of a GlcNAc residue. This new structure, the GlcNAc- Man5 - GlcNAc2 -protein, is the substrate for mannosidase II which removes the alpha 1,3- and alpha 1,6-linked mannoses . Then the other sugars, GlcNAc, galactose, and sialic acid, are added sequentially to give the complex types of glycoproteins. A number of inhibitors have been identified that interfere with glycoprotein biosynthesis, processing, or transport. Some of these inhibitors have been valuable tools to study the reaction pathways while others have been extremely useful for examining the role of carbohydrate in glycoprotein function. For example, tunicamycin and its analogs prevent protein glycosylation by inhibiting the first step in the lipid-linked pathway, i.e., the formation of Glc NAc-pyrophosphoryl-dolichol. These antibiotics have been widely used in a number of functional studies. Another antibiotic that inhibits the lipid-linked saccharide pathway is amphomycin, which blocks the formation of dolichyl-phosphoryl-mannose. In vitro, this antibiotic gives rise to a Man5GlcNAc2 -pyrophosphoryl-dolichol from GDP-[14C]mannose, indicating that the first five mannose residues come directly from GDP-mannose rather than from dolichyl-phosphoryl-mannose. Other antibodies that have been shown to act at the lipid-level are diumycin , tsushimycin , tridecaptin, and flavomycin. In addition to these types of compounds, a number of sugar analogs such as 2-deoxyglucose, fluoroglucose , glucosamine, etc. have been utilized in some interesting experiments. Several compounds have been shown to inhibit glycoprotein processing. One of these, the alkaloid swainsonine , inhibits mannosidase II that removes alpha-1,3 and alpha-1,6 mannose residues from the GlcNAc- Man5GlcNAc2 -peptide. Thus, in cultured cells or in enveloped viruses, swainsonine causes the formation of a hybrid structure.(ABSTRACT TRUNCATED AT 400 WORDS)

1-Deoxynojirimycin↗
PubMed2006

Characterization of functional oligosaccharide mimics of the Shigella flexneri serotype 2a O-antigen: implications for the development of a chemically defined glycoconjugate vaccine.

Protection against reinfection with noncapsulated Gram-negative bacteria, such as Shigella, an enteroinvasive bacterium responsible for bacillary dysentery, is mainly achieved by Abs specific for the O-Ag, the polysaccharide part of the LPS, the major bacterial surface Ag. The use of chemically defined glycoconjugates encompassing oligosaccharides mimicking the protective determinants carried by the O-Ag, thus expected to induce an efficient anti-LPS Ab response, has been considered an alternative to detoxified LPS-protein conjugate vaccines. The aim of this study was to identify such functional oligosaccharide mimics of the S. flexneri serotype 2a O-Ag. Using protective murine mAbs specific for S. flexneri serotype 2a and synthetic oligosaccharides designed to analyze the contribution of each sugar residue of the branched pentasaccharide repeating unit of the O-Ag, we demonstrated that the O-Ag exhibited an immunodominant serotype-specific determinant. We also showed that elongating the oligosaccharide sequence improved Ab recognition. From these antigenicity data, selected synthetic oligosaccharides were assessed for their potential to mimic the O-Ag by analyzing their immunogenicity in mice when coupled to tetanus toxoid via single point attachment. Our results demonstrated that induction of an efficient serotype 2a-specific anti-O-Ag Ab response was dependent on the length of the oligosaccharide sequence. A pentadecasaccharide representing three biological repeating units was identified as a potential candidate for further development of a chemically defined glycoconjugate vaccine against S. flexneri 2a infection.

Amino Acid Sequence↗
PubMed2001

[Human milk oligosaccharides. The rule in the health and development of the infants].

Breast-feeding is the optimal mode of feeding for the normal full-term infant. Human milk composition knowledge has been basis for recommended dietary allowances for infants. Few studies about human milk carbohydrates have been done until the last decade. However, carbohydrates provide approximately 40-50% of the total energy content of breast milk. Quantitatively oligosaccharides are the third largest solute in human milk after lactose and fat. Each individual oligosaccharide is based on a variable combination of glucose, galactose, sialic acid, fucose and N-acetylglucosamine with many and varied linkages between them, thus accounting for the enormous number of different oligosaccharides in human milk. The oligosaccharides content in human milk varies with the duration of lactation, diurnally and with the genetic makeup of the mother. At present, a great interest in the roles of human milk oligosaccharides is raising. They act as a the soluble fibre in breast milk and their structure is available to act as competitive ligands protecting the breast-fed infant from pathogens and act as well as prebiotic. They may also act as source of sialic acid and galactose, essential for brain development. This is why today there is an increasing health and industrial interest in human milk oligosaccharides content, with the main purpose of incorporating them as new ingredients in infant nutrition.

Animals↗
PubMed1992

Lysosomal enzyme phosphorylation. II. Protein recognition determinants in either lobe of procathepsin D are sufficient for phosphorylation of both the amino and carboxyl lobe oligosaccharides.

Cathepsin D is a bilobed lysosomal aspartyl protease that contains one Asn-linked oligosaccharide/lobe. Each lobe also contains protein determinants that serve as recognition domains for binding of UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase, the first enzyme in the biosynthesis of the mannose 6-phosphate residues on lysosomal enzymes. In this study we examined whether the location of the protein recognition domain influences the relative phosphorylation of the amino and carboxyl lobe oligosaccharides. To do this, chimeric proteins containing either amino or carboxyl lobe sequences of cathepsin D substituted into a glycosylated form of the homologous secretory protein pepsinogen were expressed in Xenopus oocytes. The amino and carboxyl lobe oligosaccharides were then isolated from the various chimeric proteins and independently analyzed for their mannose 6-phosphate content. This analysis has shown that a phosphotransferase recognition domain located on either lobe of a cathepsin D/glycopepsinogen chimeric molecule is sufficient to allow phosphorylation of oligosaccharides on both lobes. However, phosphorylation of the oligosaccharide on the lobe containing the recognition domain is favored. We also found that the majority of the carboxyl lobe oligosaccharides of cathepsin D acquire two phosphates, whereas the amino lobe oligosaccharides only acquire one phosphate.

Animals↗
PubMed1992

The asparagine-linked oligosaccharides on tissue factor pathway inhibitor terminate with SO4-4GalNAc beta 1, 4GlcNAc beta 1,2 Mana alpha.

Tissue factor pathway inhibitor (TFPI) produced by endothelial cells contains sulfated Asn-linked oligosaccharides. We have determined that greater than 70% of the oligosaccharides on recombinant TFPI expressed in 293 cells terminate with the sequence SO4-4GalNAc beta 1, 4GlcNAc beta 1, 2Man alpha. Oligosaccharides terminating with this sequence have previously been described on lutropin, thyrotropin, and pro-opiomelanocortin: glycoproteins synthesized in the anterior pituitary. A GalNAc-transferase that recognizes the tripeptide motif Pro-Xaa-Arg/Lys 6-9 residues N-terminal to Asn glycosylation sites accounts for the specific addition of GalNAc to the oligosaccharide acceptor on these glycoproteins, whereas a GalNAc beta 1,4GlcNAc beta 1, 2Man alpha-4-sulfotransferase accounts for the addition of sulfate. The sulfated oligosaccharides present on these hormones are responsible for their rapid clearance from plasma by a receptor in hepatic reticuloendothelial cells. GalNAc- and sulfotransferase activities with the same properties as those expressed in the pituitary are detected at high levels in 293 cells and at lower levels in endothelial cells. Chinese hamster ovary (CHO) cells do not contain detectable levels of either transferase and rTFPI expressed in CHO cells does not contain sulfated Asn-linked oligosaccharides. TFPI contains the sequence Pro-Phe-Lys, 9 residues N-terminal to the glycosylation site at position 228; this tripeptide may act as the recognition sequence for the GalNAc-transferase. rTFPI produced by 293 cells, but not that produced by CHO cells, is bound by the receptor on hepatic reticuloendothelial cells suggesting the sulfated structures play a role in the biologic behavior of TFPI.

Acetates↗
PubMed2005

[Preparation of oligosaccharides from alginate by fermenting combined with membrane separation method and analysis of the oligomers].

Changes in biomass, oligosaccharides content and alginate lyase activity in broth of Alteromonas sp. incubated in shaking flask and fermentation jar were studied. According to those changes, parameters were established for preparing oligosaccharides from alginate by fermentation combined with nano-filtration membrane separation method. Resulting oligosaccharides were analyzed by gel permeation chromatography and thin layer chromatography. One liter culture medium(pH 7.5) contains 5 g yeast extract, l0 g peptone, 0.1 g FeSO4, 12 g sodium alginate and 1.5 g NaCl. When incubating at 28 degrees C, the result showed that the optimal fermentation time was 30 h to obtain the highest production of oligosaccharides in the broth. After ultra-filtration and nano-filtration, 94.0% of the total oligosaccharides was recovered from the broth, and meanwhile 93.3% of the salt was removed. Gel permeation chromatography and TLC analyses indicated that the resulting oligosaccharides were composed of five fractions with different degree of polymerization.

Alginates↗
PubMed1992

Pro-opiomelanocortin synthesized by corticotrophs bears asparagine-linked oligosaccharides terminating with SO4-4GalNAc beta 1,4GlcNAc beta 1,2Man alpha.

We have determined that greater than or equal to 80% of the Asn-linked oligosaccharides on the glycosylated form of mouse adrenocorticotropin (15-kDa adrenocorticotropin (ACTH)) bear one or more branches terminating with the sequence SO4-4GalNAc beta 1,4GlcNAc beta 1,2Man alpha (S4GGnM). Proopiomelanocortin (POMC), the precursor of ACTH, is the first example of a glycoprotein that is not a member of the glycoprotein hormone family to bear such sulfated structures. Like lutropin and thyrotropin, 15-kDa ACTH bears dibranched oligosaccharides terminating with SO4-4-GalNAc; however, at least half of the oligosaccharides on 15-kDa ACTH terminating with SO4-4-GalNAc consist of more highly branched structures that have not previously been described. Both the GalNAc beta 1,4GlcNAc beta 1,2Man-4-sulfotransferase and the glycoprotein hormone-specific GalNAc-transferase are expressed in the corticotroph-derived AtT-20 cell line. A tripeptide recognition sequence, Pro-Val-Lys, similar to the Pro-Leu-Arg sequence required for recognition of glycoprotein hormone alpha- and beta-subunits by the glycoprotein hormone-specific GalNAc-transferase, is present 8 residues amino-terminal to the glycosylated Asn of 15-kDa ACTH. Thus, POMC has the features expected for specific addition of the S4GGnM sequence to its oligosaccharides. The recent discovery of a receptor in hepatic endothelial cells that recognizes oligosaccharides terminating with S4GGnM suggests these sulfated oligosaccharides will regulate the circulatory half-life of glycosylated POMC cleavage products.

Amino Acid Sequence↗
PubMed1991

Structure of oligosaccharides on Saccharomyces SUC2 invertase secreted by the methylotrophic yeast Pichia pastoris.

Saccharomyces SUC2 invertase, secreted by the methylotrophic yeast Pichia pastoris and purified to homogeneity from the growth medium by DE-52 chromatography, appeared on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a diffuse ladder of species at 85-90 kDa, while the secreted Saccharomyces form migrated as a broad band from 100 to 150 kDa. Endo-beta-N-acetylglucosaminidase H released the Pichia invertase carbohydrate generating a 60-kDa protein with residual Asn-linked GlcNAcs and oligosaccharides separated on Bio-Gel P-4 into Man8-11GlcNAc. Nearly 75% of the oligosaccharides were equally distributed between Man8,9GlcNAc, while 17% were Man10GlcNAc and 8% were Man11GlcNAc. Oligosaccharide pools were analyzed for homogeneity by high-pH anion-exchange chromatography, and structures were assigned using 500 MHz one- and two-dimensional 1H NMR spectroscopy. Pichia Man8GlcNAc was the same isomer as found in Saccharomyces, which arises by removing the alpha 1,2-linked terminal mannose from the middle arm of the lipid-oligosaccharide Man9GlcNAc (Byrd, J. C., Tarentino, A. L., Maley, F., Atkinson, P. H., and Trimble, R. B. (1982) J. Biol. Chem. 257, 14657-14666). The Man9GlcNAc pool was 5% lipid-oligosaccharide precursor and 95% Man8GlcNAc isomer with a terminal alpha 1,6-linked mannose on the lower-arm alpha 1,3-core-linked residue (Hernández, L. M., Ballou, L., Alvarado, E., Gillece-Castro, B. L., Burlingame, A. L., and Ballou, C. E. (1989) J. Biol. Chem. 264, 11849-11856). An alpha 1,2-linked mannose on the new alpha 1,6-linked branch in Man9GlcNAc provided 80% of the Man10GlcNAc, which is the structure on Saccharomyces invertase (Trimble, R. B., and Atkinson, P. H. (1986) J. Biol. Chem. 261, 9815-9824). A minor Man10GlcNAc (12%) and the principal Man11GlcNAc (82%) were the major Man9,10GlcNAc with novel alpha 1,2-linked mannoses on the preexisting alpha 1,2-linked termini. Although Pichia glycans did not have terminal alpha 1,3-linked mannoses as found on Saccharomyces core oligosaccharides, over 60% of the structures were isometric configurations unique to lower eukaryotes.

Carbohydrate Sequence↗
PubMed1991

Structure of Saccharomyces cerevisiae alg3, sec18 mutant oligosaccharides.

Asparagine-linked oligosaccharides are synthesized by transfer of Glc3Man9GlcNAc2 from dolichol pyrophosphate to nascent polypeptides. Assembly of the precursor proceeds by highly ordered sequential addition of mannose and glucose to form Glc3Man9GlcNAc2-P-P-dolichol. Yeast mutants in asparagine-linked glycosylation (alg), generated by an 3H-Man suicide technique, were assigned to eight complementation groups which define steps in oligosaccharide-lipid synthesis (Huffaker, T.C., and Robbins, P.W. (1982) J. Biol. Chem. 257, 3203-3210). Alg3 invertase oligosaccharides are resistant to endo-beta-N-acetylglucosaminidase H, and the lipid-oligosaccharide pool yields Man5Glc-NAc2, suggesting its structure may be that from mammalian cells lacking Man-P-dolichol (Chapman, A., et al. (1980) J. Biol. Chem. 255, 4441-4446). To test this supposition, the endoplasmic reticulum form of invertase derepressed in alg3,sec18 yeast at 37 degrees C was isolated as a source of oligosaccharides whose processing beyond glucose and/or mannose trimming, if involved, would be prevented. Man8GlcNAc2 and Man5GlcNAc2 were released by peptide-N-glycosidase F from alg3,sec18 invertase in a 1:5 molar ratio. 1H NMR spectroscopy revealed Man8GlcNAc2 to be the alpha 1,2-mannosidase-trimming product described earlier (Byrd, J. C., Tarentino, A. L., Maley, F., Atkinson, P. H., and Trimble, R. B. (1982) J. Biol. Chem. 257, 14657-14666), while Man5GlcNAc2 was Man alpha 1, 2Man alpha 1,2Man alpha 1,3(Man alpha 1,6)Man beta 1,4GlcNAc beta 1, 4GlcNAc. This provides a structural proof for the lipid-linked Man5GlcNAc2 originally proposed from enzymatic and chemical analyses of the radiolabeled mammalian precursor. Experimental evidence indicates that, unlike the mammalian cell mutants which are unable to synthesize Man-P-dolichol, alg3 yeast accumulate Man5GlcNAc2-P-P-dolichol due to a defective alpha 1,3-mannosyltransferase required for the next step in oligosaccharide-lipid elongation.

Carbohydrate Conformation↗
PubMed1990

Sulfated N-linked oligosaccharides affect secretion but are not essential for the transport, proteolytic processing, and sorting of lysosomal enzymes in Dictyostelium discoideum.

Although previous studies have indicated that N-linked oligosaccharides on lysosomal enzymes in Dictyostelium discoideum are extensively phosphorylated and sulfated, the role of these modifications in the sorting and function of these enzymes remains to be determined. We have used radiolabel pulse-chase, subcellular fractionation, and immunofluorescence microscopy to analyze the transport, processing, secretion, and sorting of two lysosomal enzymes in a mutant, HL244, which is almost completely defective in sulfation. [3H]Mannose-labeled N-linked oligosaccharides were released from immunoprecipitated alpha-mannosidase and beta-glucosidase of HL244 by digestion with peptide: N-glycosidase. The size, Man9-10GlcNAc2, and processing of the neutral species were similar to that found in the wild type, but the anionic oligosaccharides were less charged than those from the wild-type enzymes. All of the negative charges on the oligosaccharides for HL244 were due to the presence of 1, 2, or 3 phosphodiesters and not to sulfate esters. The rate of proteolytic processing of precursor forms of alpha-mannosidase and beta-glucosidase to mature forms in HL244 was identical to wild type. The precursor polypeptides in the mutant and the wild type were membrane associated until being processed to mature forms; therefore, sulfated sugars are not essential for this association. Furthermore, the rate of transport of alpha-mannosidase and beta-glucosidase from the endoplasmic reticulum to the Golgi complex was normal in the mutant as determined by the rate at which the newly synthesized proteins became resistant to the enzyme, endo-beta-N-acetylglucosaminidase H. There was no increase in the percentage of newly synthesized mutant precursors which escaped sorting and were secreted, and the intracellularly retained lysosomal enzymes were properly localized to lysosomes as determined by fractionation of cell organelles on Percoll gradients and immunofluorescence microscopy. However, the mutant secreted lysosomally localized mature forms of the enzymes at 2-fold lower rates than wild-type cells during both growth and during starvation conditions that stimulate secretion. Furthermore, the mutant was more resistant to the effects of chloroquine treatment which results in the missorting and oversecretion of lysosomal enzymes. Together, these results suggest that sulfation of N-linked oligosaccharides is not essential for the transport, processing, or sorting of lysosomal enzymes in D. discoideum, but these modified oligosaccharides may function in the secretion of mature forms of the enzymes from lysosomes.

Acetylglucosaminidase↗
PubMed1978

A novel phosphodiesterase from Aspergillus niger and its application to the study of membrane-derived oligosaccharides and other glycerol-containing biopolymers.

A novel phosphodiesterase has been found in commercially available extracts of Aspergillus niger and has been partially purified by fractionation with acetone and chromatography on carboxymethylcellulose. The enzyme attacks glycerophosphodiester bonds with the liberation of free glycerol only. The synthetic substrate glucose 6-phospho-sn-1'(3')-glycerol is hydrolyzed with production of equivalent amounts of free glycerol and glucose 6-phosphate. Similarly, the enzymic hydrolysis of sn-glycero-3-phosphocholine liberates glycerol and phosphocholine. The hydrophilic head groups of membrane phospholipids of Escherichia coli are continuously transferred to a closely related family of oligosaccharides ("membrane-derived oligosaccharides") containing glucose as the sole sugar (van Golde, L. M. G., Schulman, H., and Kennedy, E. P. (1973) Proc. Natl. Acad. Sci. U. S. A. 70, 1368--1372). Oligosaccharide A-2 contains sn-1-glycerophosphate residues (derived from phosphatidylglycerol) in phosphodiester linkage. Treatment of this oligosaccharide with the phosphodiesterase led to the liberation of nearly all of the glycerol as free glycerol. Subsequent partial acid hydrolysis of the enzyme-treated oligosaccharide led to the recovery of glucose 6-phosphate in almost quantitative yield. The sn-1-glycerophosphate residues are therefore linked to position 6 of glucose units of the oligosaccharide. The activity of the enzyme is not restricted to glycerophosphodiesterases since it will hydrolyze phosphodiesters containing other polyols such as the synthetically prepared glucose 6-phospho-DL-1'(2'-hydroxy-3'-ethoxy)propane.

Aspergillus niger↗
PubMed1990

The sialylated oligosaccharides of recombinant bovine lutropin modulate hormone bioactivity.

The Asn-linked oligosaccharides from bovine lutropin (bLH(Pit] are predominantly dibranched complex-type structures with the terminal sequence SO4-4GalNAc beta 1,4GlcNAc beta 1,2Man alpha. Recombinant bLH expressed in Chinese hamster ovary cells (bLH(CHO] bears di- (60%) and tribranched (30%) complex-type oligosaccharides; however, these terminate in the sequence Sia alpha 2,3Gal beta 1,4GlcNAc beta 1,2Man alpha. In contrast to the limited spectrum of oligosaccharide structures present on recombinant bLH(CHO), the endogenous glycoproteins synthesized by CHO cells bear a heterogeneous array of Asn-linked oligosaccharides with 0, 1, 2, 3, or 4 sialic acid moieties. The sialic acid moieties on the Asn-linked oligosaccharides of both endogenous glycoproteins and recombinant bLH(CHO) are exclusively alpha 2,3-linked, suggesting that the alpha 2,6-sialyl-transferase is not active in CHO cells. The bioactivities of bLH(Pit) and bLH(CHO) were compared using MA-10 cells following sequential digestion with neuraminidase and beta-galactosidase. Neither the ED50 (dose producing 50% of the maximum response) for progesterone production (7.2 ng/ml) nor the Pmax (maximum level of progesterone produced) (470 ng/ml) was altered for bLH(Pit) by these treatments, consistent with the absence of either sialic acid or Gal on bLH(Pit). The ED50 for progesterone production by recombinant bLH(CHO) (16.4 ng/ml) was significantly greater than for bLH(Pit) but was reduced to 5.3 ng/ml following removal of terminal sialic acid. Removal of the subterminal Gal was without further effect. The Pmax for bLH(CHO) (180 ng/ml) was not altered by these treatments. The reduction in bLH(CHO) bioactivity caused by the presence of terminal sialic acid suggests that the presence of terminal sulfate on bLH(Pit) oligosaccharides may also reduce its bioactivity and may play a modulatory role in regulating hormone bioactivity.

Animals↗