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PubMed1999

Identification of a new glycosylphosphatidylinositol-anchored 42-kDa protein and its C-terminal peptides from bovine erythrocytes by gas chromatography-, time-of-flight-, and electrospray-ionization-mass spectrometry.

By treatment with phosphatidylinositol-specific phospholipase C (PIPLC), we obtained several candidates of glycosylphosphatidylinositol (GPI)-anchored proteins such as 55, 42, 40, and 30 kDa from bovine erythrocyte membrane, in addition to the well-known GPI-anchored protein acetylcholinesterase. In these proteins, the presence of myo-inositol was confirmed by gas chromatography (GC)-mass spectrometry. Among them, the 42-kDa protein was further analyzed by electrospray-ionization (ESI)-mass spectrometry (MS) after hydrolysis by lysyl endoprotease. By liquid chromatography (LC)-ESI-MS analysis, C-terminal peptides bearing the products of GPI (Ct. GPI-peptides) were effectively detected by combination with in-source collision and multifunctional scanning for the several characteristic fragment ions from the GPI-anchor structure. Existence of microheterogeneity was also observed in the Ct. GPI-peptides from the 42-kDa protein. This result was confirmed by analysis with time-of-flight (TOF)-MS. Furthermore, one of the Ct. GPI-peptides was analyzed in ESI-MS-MS mode. Characteristic fragment ions were effectively detected by collision-induced decay. By the result of MS-MS analysis, this GPI-anchor structure was revealed to contain additional N-acetyl hexosamine. By the above-mentioned method, the C-terminal GPI-anchor structure can be easily identified from the target protein even if its amino acid sequence data are not available.

Acetylcholinesterase↗
PubMed2000

Purification and characterization of glutamine:fructose 6-phosphate amidotransferase from rat liver.

The enzyme glutamine:fructose 6-phosphate amidotransferase (L-glutamine:D-fructose-6-phosphate amidotransferase; EC 2.6.1.16, GFAT) catalyzes the formation of glucosamine 6-phosphate from fructose 6-phosphate and glutamine. In view of the important role of GFAT in the hexosamine biosynthetic pathway, we have purified the enzyme from rat liver and characterized its physicochemical properties in comparison to those from the published microbial enzymes. The purified enzyme has a molecular mass of about 75 kDa as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. On a Sephacryl S-200 gel filtration column, the purified enzyme eluted in a single peak corresponding to a molecular mass of about 280 kDa, indicating that the active enzyme may be composed of four subunits. The N-terminal amino acid sequence of the purified enzyme was determined as X-G-I-F-A-Y-L-N-Y-H-X-P-R, where X indicates an unidentified residue. The K(M) values of the purified enzyme for fructose 6-phosphate and glutamine were 0.4 and 0.8 mM, respectively. The purified enzyme was inactivated by 4, 4'-dithiodipyridine, and the activity of the inactivated enzyme was restored by dithiothreitol. The inactivation followed pseudo first-order and saturation kinetics with the K(inact) of 5.0 microM. Kinetic studies also indicated that 4,4'-dithiodipyridine is a competitive inhibitor of the enzyme with respect to glutamine. Isolation and analysis of the cysteine-modified peptide indicated that Cys-1 was the modified site. Cys-1 has been suggested to play an important role in enzymatic activity of the Escherichia coli enzyme (M. N. Isupov, G. Obmolova, S. Butterworth, M. Badet-Denisot, B. Badet, I. Polikarpov, J. A. Littlechild, and A. Teplyakov, 1996, Structure 4, 801-810).

Amino Acid Sequence↗
PubMed2001

Hyperglycemia and the O-GlcNAc transferase in rat aortic smooth muscle cells: elevated expression and altered patterns of O-GlcNAcylation.

Hyperglycemia leads to vascular disease specific to diabetes mellitus. This pathology, which results from abnormal proliferation of smooth muscle cells in arterial walls, may lead to cataract, renal failure, and atherosclerosis. The hexosamine biosynthetic pathway is exquisitely responsive to glucose concentration and plays an important role in glucose-induced insulin resistance. UDP-GlcNAc: polypeptide O-N-acetylglucosaminyltransferase (O-GlcNAc transferase; OGTase) catalyzes the O-linked attachment of single GlcNAc moieties to serine and threonine residues on many cytosolic or nuclear proteins. Polyclonal antibody against OGTase was used to examine the expression of OGTase in rat aorta and aortic smooth muscle (RASM) cells. OGTase enzymatic activity and expression at the mRNA and protein levels were determined in RASM cells cultured at normal (5 mM) and at high (20 mM) glucose concentrations. OGTase mRNA and protein are expressed in both endothelial cells and smooth muscle cells in the aorta of normal rats. In both cell types, the nucleus is intensely stained, while the cytoplasm stains diffusely. Immunoelectron microscopy shows that OGTase is localized to euchromatin and around the myofilaments of smooth muscle cells. In RASM cells grown in 5 mM glucose, OGTase is also located mainly in the nucleus. Hyperglycemic RASM cells also display a relative increase in OGTase's p78 subunit and an overall increase protein and activity for OGTase. Biochemical analyses show that hyperglycemia qualitatively and quantitatively alters the glycosylation or expression of many O-GlcNAc-modified proteins in the nucleus. These results suggest that the abnormal O-GlcNAc modification of intracellular proteins may be involved in glucose toxicity to vascular tissues.

Animals↗
PubMed1994

Microscale analysis of glycosphingolipids by methanolysis, peracetylation, and gas chromatography.

A method for the analysis of pure samples of individual glycosphingolipids by microscale methanolysis, peracetylation, and gas chromatography is described. Solvolysis of glycosphingolipids in dry methanolic HCl and peracetylation were conducted in a single 4.5-cm sealed capillary tube (2 mm i.d.), after which the products were directly injected into a gas chromatograph. Total-component analysis (i.e., analysis of the sugar, fatty acid, and sphingosine moieties) was possible after a 45-min chromatographic run. Time-course studies of the acid-catalyzed methanolysis of Gal beta 1-4GalNAc beta 1-4(NeuAc alpha 2-3)Gal beta 1-4Glc beta 1-1Cer ganglioside at 80, 110, and 150 degrees C showed that methanolysis was complete after 2 h at 110 degrees C. Rates of methanolysis of individual components were compared and the release of the fatty acid moiety from the long-chain base was shown to be the slowest reaction. The methanolysis of all glycosidic bonds were complete in 0.5 h. Peracetylated methanolysis products were very stable over time and provided for good gas chromatographic detection of subnanomolar amounts of hexose, hexosamine, fatty acid, sialic acid, and long-chain sphingoid base components. Recoveries of fucose and N-acetylglucosamine were determined with reference samples of Fuc alpha 1-2Lac and lacto-N-fucosylpentaose II. Applications of the method are presented for the component analysis of a gift mixture of NeuAc alpha 2-6Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-1Cer ganglioside and NeuAc alpha 2-6Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-4Glc-Cer ganglioside and analysis of NeuAc alpha 2-3Gal beta 1-4Glc beta 1-1Cer isolated from human plasma.

Acetylation↗
PubMed1999

A pyridylamination method aimed at automatic oligosaccharide analysis of N-linked sugar chains.

The procedure for preparation of pyridylaminated sugar chains from glycoproteins was improved with a view to its eventual automation. Following on the coupling reaction improvement already reported [N. Kuraya and S. Hase (1992) J. Biochem. 112, 122-126], two further aspects were improved in this study. Instead of sodium bicarbonate-acetic anhydride, volatile reagents were adopted for the re-N-acetylation of hexosamine residues after hydrazinolysis to give rapid removal of excess reagents. Subsequent to the pyridylamination reaction, excess reagents were removed by cation-exchange to isolate the pyridylaminated oligosaccharides in place of gel filtration. These alterations rendered a one-pot reaction possible and resulted in a large reduction in the amount of time needed compared with other methods so far reported. The procedure was successfully applied to the detection of sugar chains from Taka-amylase A and human erythrocyte membranes.

Aminopyridines↗
PubMed1999

A single-sample method for determination of carbohydrate and protein contents glycoprotein bands separated by sodium dodecyl sulfate- polyacrylamide gel electrophoresis.

A method is described for determination of carbohydrate and protein contents of glycoproteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and then electroblotted onto polyvinylidene difluoride (PVDF) membranes. Blots were stained, and appropriate pieces of PVDF membranes were excised, destained, and subjected to sequential hydrolysis with 0.2 M trifluoroacetic acid (TFA) for 1 h at 80 degrees C, then with 2 M TFA for 4 h at 100 degrees C, and finally with 6 M HCl at 100 degrees C for 24 h to release sialic acids, neutral sugars with hexosamines, and amino acids, respectively. In some instances preliminary methanolysis was used. Carbohydrates including sialic acids were quantitated by high pH anion exchange chromatography with pulsed amperometric detection. Protein content of the bands was determined as amino acids by the fluorescamine or ninhydrin method. In the calculation of results proper adjustments were made for small amounts of fucose released by hydrolysis with 0.2 M TFA at 80 degrees C, and for partial degradation of protein during hydrolysis with 2 M TFA at 100 degrees C. Recoveries of amino acids from hydrolysates of glycoproteins that had been electroblotted onto PVDF membranes equaled those of carbohydrates. This was possible because of preliminary hydrolysis of glycoproteins with TFA, as well as washing of wet, instead of dried, PVDF membranes after hydrolysis with 6 M HCl. The two modifications increased yields of amino acids by about 30%. The method was successfully applied to the determination of molar and weight percentage composition of human transferrin, band 3 protein, glycophorin A, and alpha(1)-acid glycoprotein. In each case the results obtained for directly hydrolyzed and electrophoresed/electroblotted glycoproteins were practically identical. We also determined the glucosamine content of band 4.1 protein of erythrocytes.

Carbohydrates↗
PubMed1999

Elevated expression of free deaminoneuraminic acid in mammalian cells cultured in mannose-rich media.

Deaminoneuraminic acid (KDN, 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid) is a member of the family of sialic acids in which an acylamino group at the C-5 position of N-acylneuraminic acid (Neu5Acyl) is replaced by a hydroxyl group. It has recently been shown that KDN is synthesized de novo from its precursor, mannose (Man), in trout testis (Angata, T., Nakata, D., Matsuda, T., Kitajima, K., and Troy, F. A. (1999) J. Biol. Chem. 274, in press). In this study, we examined the effect of extracellular free Man on biosynthesis of KDN in mouse melanoma B16 and African green monkey kidney COS-7 cell lines. The following new findings are reported. First, the levels of free and bound forms of KDN increased when the cells were cultured in the presence of 20 mM Man. The level of intracellular free KDN in COS-7 and B16 cells increased 47- and 66-fold respectively, compared with the levels in control cells. Second, the elevated expression of free KDN was proportional to the intracellular concentration of free Man. Third, KDN 9-phosphate (KDN-9-P) synthase, which condenses Man 6-phosphate and phosphoenolpyruvate (PEP), forming KDN-9-P, was detected in cell lysates from both cell lines. Fourth, the de novo synthesis of KDN in both cell lines in the Man-rich media was unaffected by the addition of N-acetylmannosamine (ManNAc), the hexosamine precursor for synthesis of N-acetylneuraminic acid (Neu5Ac). These results show that KDN is synthesized using free Man as its hexose precursor in these mammalian cells. Thus, the KDN biosynthetic pathway utilizes enzymes distinct, at least in part, from those involved in Neu5Ac biosynthesis. This is the first report showing that in vivo synthesis of KDN can be manipulated by growing cells in the presence of Man. This now provides a useful method to study the metabolism and function of the KDN glycotope.

Animals↗
PubMed1999

cDNA cloning and mapping of a novel subtype of glutamine:fructose-6-phosphate amidotransferase (GFAT2) in human and mouse.

We subcloned human and mouse full-length cDNAs of a novel subtype of glutamine:fructose-6-phosphate amidotransferase (GFAT), which was designated GFAT2 (the previously reported GFAT was named GFAT1). Both the human and the mouse GFAT2 proteins deduced from their open reading frame sequences are composed of 682 amino acids of approximately 77.0 kDa. At the amino acid level, homologies between the human GFAT1 and GFAT2, between the mouse GFAT1 and GFAT2, and between the human GFAT2 and the mouse GFAT2 were 75.6, 74.7, and 97. 2%, respectively. Northern blot analysis using probe specific to human GFAT1 or GFAT2 showed that major transcripts were approximately 3.0 kb in both the human GFAT subtypes. The analysis also revealed different tissue distribution between GFAT1 and GFAT2: GFAT1 was more highly expressed in the placenta, pancreas, and testis than GFAT2; GFAT2 was expressed throughout the central nervous system, especially in the spinal cord, but GFAT1 expression was weak. The locus was mapped to human chromosome 5q and mouse chromosome 11, where a synteny between the two species has been known. GFAT2 can provide insights into understanding the roles of the hexosamine pathway in various tissues, particularly with the development of glucose toxicity and diabetes complications.

Amino Acid Sequence↗
PubMed2001

Channeling of ammonia in glucosamine-6-phosphate synthase.

Glucosamine-6-phosphate synthase catalyses the first and rate-limiting step in hexosamine metabolism, converting fructose 6-phosphate into glucosamine 6-phosphate in the presence of glutamine. The crystal structure of the Escherichia coli enzyme reveals the domain organisation of the homodimeric molecule. The 18 A hydrophobic channel sequestered from the solvent connects the glutaminase and isomerase active sites, and provides a means of ammonia transfer from glutamine to sugar phosphate. The C-terminal decapeptide sandwiched between the two domains plays a central role in the transfer. Based on the structure, a mechanism of enzyme action and self-regulation is proposed. It involves large domain movements triggered by substrate binding that lead to the formation of the channel.

Ammonia↗
PubMed1988

Biochemistry and lectin binding properties of mammalian salivary mucous glycoproteins.

The molecules responsible for the highly viscous properties of mucus are secretory glycoproteins referred to as mucins. Salivary mucins are characterized by a high sugar to protein ratio and are of a broad range of molecular weight from 7 x 10(4) to millions. With a few exceptions, they contain up to 30% of hexosamine (galactosamine and glucosamine), 8-33% of sialic acid, trace to 15% of galactose or fucose and little or no mannose. The size of carbohydrate side chains of these glycoproteins ranges from one to about fifteen units of sugar. These carbohydrate side chains are usually O-glycosidically linked through N-acetylgalactosamine to a peptidyl serine or threonine. In some instances, ester sulfate groups, mainly on N-acetylglucosamine, are also a structural feature. In many of these glycoproteins, the saccharide sequence is the same as that which determines the specificity of blood groups. Carbohydrate sequence analysis shows that salivary mucins exhibit considerable polydispersity, great diversity and remarkable structural flexibility not only among animal species but also within the same mucin molecule. Based on their lectin-binding ability, they can be used for purification of lectins, and lectins coupled to resin may be useful for the isolation of mucin-type glycoproteins. The epithelial mucous secretions modulate oral microbial flora; many secretory components serve as lectin-receptors for the attachment of microbes. The judicious use of lectins with widely differing binding characteristics has already been valuable in the in situ localization of salivary glycoproteins, in elucidating structural details, recording sugar density within a given tissue section, and defining host-parasite interactions. It is hoped that their use, together with monoclonal antibody (158) and tissue culture techniques (159, 160) will further clarify the roles of individual secretory mucous glycoproteins in health and disease.

Animals↗
PubMed1995

Isolation and characterization of exocellular polysaccharides produced by Bifidobacterium longum.

When grown anaerobically at pH values above 5.0, on ultrafiltered complex media containing excess lactose, Bifidobacterium longum formed up to 140 mg l-1 (glucose equiv.) exopolysaccharides. The highest yield was obtained when the cells were cultivated in a peptone/yeast extract medium with pH controlled by additions of NH4OH. Whatever the conditions under study, exopolysaccharides represented about 30% of the polysaccharides produced by B. longum after 48 h of culture. Crude pronase-treated exopolysaccharide preparations were adsorbed on ion-exchange chromatographic resin to yield an anionic heteropolysaccharide fraction. Two subfractions with apparent molecular masses of 1.2 MDa and 0.36 MDa respectively were subsequently recovered after gel filtration on Sepharose 4B. In both subfractions, glucose, galactose and small amounts of uronic acids and hexosamines were present in similar molar proportions, suggesting that the excreted polymers may be synthesized from the same base unit and may have a structure resulting from repeating subunits.

Anaerobiosis↗
PubMed1995

Human glutamine: fructose-6-phosphate amidotransferase: characterization of mRNA and chromosomal assignment to 2p13.

It has been previously shown that some toxic effects of high concentrations of glucose are mediated by the hexosamine biosynthesis pathway and its rate-limiting enzyme glutamine:fructose-6-phosphate amidotransferase (GFA). We have used the cloned human GFA cDNA to study the chromosomal localization of the gene and tissue distribution of mRNA. The human GFA gene is on chromosome 2, band p13 as determined by fluorescence in situ hybridization. An 8-kb species of GFA mRNA was detected in all rat tissues tested with relatively high expression in testis and smooth muscle; a unique 3-kb mRNA species was found only in testis.

Animals↗
PubMed1983

Glycosaminoglycans in urothelial carcinomas.

The glycosaminoglycan (GAG) content in human urothelial carcinomas was biochemically determined and compared to that of normal urothelium and bladder wall of the calf. The total GAG content was elevated in urothelial carcinomas, and the distribution pattern differed from that of normal urothelium and bladder wall. Whereas urothelial carcinomas contained heparan sulphate, dermatan sulphate, chondroitin 4-sulphate and chondroitin 6-sulphate, only heparan sulphate could be detected in the normal urothelium. The GAG determination was based on hexosamine analysis and thin layer chromatography after elution on Dowex 1 X 2 columns.

Aged↗
PubMed1981

The phosphoenolpyruvate-dependent carbohydrate: phosphotransferase system enzymes II as chemoreceptors in chemotaxis of Escherichia coli K 12.

In Escherichia coli K12, eight substrate-specific, membrane-bound enzymes II of the PEP-dependent carbohydrate: phosphotransferase system (PTS), specific for hexoses, hexosamines and hexitols, have been characterised in a series of isogenic and constitutive strains. In such mutants, lacking all but one enzyme II, the transport and vectorial phosphorylation activities as well as the chemotactical response in capillary tube assays have been compared. According to the data obtained, all enzymes II not only are directly involved in the transport and vectorial phosphorylation of their substrates, but they have also a primary role as the chemoreceptors for these substrates: (1) Metabolism of the attractant beyond the phosphorylation step is not a pre-requisite to eliciting positive chemotaxis. (2) Mutants, having only one enzyme II react in the capillary tube assay only to substrates of this enzyme II, but not to substrates of the missing enzymes II. This holds for enzymes II consisting of one membrane-bound protein as well as for systems containing a soluble factor III (FIII). (3) The substrate specificities or affinities, whether tested by transport and chemotaxis assays in vivo or by phosphorylation tests in vitro, are in correspondence. (4) The activities of enzymes II, regulated in a complex way at the level of enzyme synthesis and activity and tested as above, are also in agreement, (5) Mutants lacking the soluble proteins enzyme I or HPr of the PTS no longer respond chemotactically to any substrate taken up and phosphorylated by enzymes II. It is concluded that in PTS enzymes II some functions required for transport and chemotaxis are identical. It is suggested furthermore, that the alternation of intrinsic membrane-bound proteins between a phosphorylated and a dephosphorylated state, rather than binding of the substrate to the enzyme II, is the decisive stimulus in the chemotaxis toward carbohydrates taken up by these transport systems.

Bacterial Proteins↗
PubMed1992

The effects of caffeine on the maxillary composition in the newborn rat.

The possible influence of caffeine on maxillary structure was studied. Seventeen pregnant rats at days 9 of gestation were randomly divided into two groups. The dams of group 1 received a 20% protein diet ad libitum throughout the experimental period. The dams of group 2 were pair-fed, with group 1, a 20% protein diet supplemented with 2 mg/100 g body weight (B.W.) caffeine. At birth, pups were mixed within the same group and 8 randomly selected pups were assigned to each dam and continuously fed the respective diet. On day 22, 11 male pups from the control and 12 males from the caffeine group were randomly selected, separated from the dams, and continued to be fed their respective diets. On day 44, a rubber elastic band was inserted between the first and second maxillary right molars. The size of the elastic band was increased throughout the next 5 days. Animals were sacrificed at day 49 and the composition of the maxillas was analyzed. After pulverization, organic and inorganic contents of the bones were measured. Zinc (Zn) and hydroxyproline concentration of the caffeine group showed a significant decrease when compared with those of the controls. However, Ca, P, Mg, and hexosamine concentration showed no difference between the groups. The interdental space measured occlusally and laterally with the visual method, and occlusally in histological sections showed no significant difference between the control and caffeine groups, although variation of the space in the caffeine group was less than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Adult type mucolipidosis with beta-galactosidase and sialidase deficiency. Histological and biochemical studies.

A case of adult type mucolipidosis with beta-galactosidase and sialidase deficiency is described. This patient, a woman aged 20, had mental retardation, macular cherry-red spots, corneal clouding, gargoyle-like face, cerebellar ataxia, myoclonus and convulsions beginning at the age of 14. Bony deformities, vacuoles in the peripheral lymphocyte and foamy cells in the bone marrow were also noted. Biopsy study of the sural nerve and vermiform appendix disclosed many vacuoles in almost every kind of cells, although the accumulated substance in these vacuoles could not be characterized histochemically or ultrastructurally. Deficient leukocyte beta-galactosidase and sialidase were confirmed. There was increased urinary sialoglycopeptide and increased siliac acid and hexosamine in the glycoprotein of lymphocytes. Leukocytes sialidase activites of the parents were 30 to 50% of the control values. These results suggest a genetic defect of sialidase.

Adult↗
PubMed1975

[Inhibition of corneal metabolism by glucocorticosteroids. An in vitro study (author's transl)]?14Hemmung des Hornhautstoffwechals durch Glukocorticosteroide. Eine in vitro Studie.

Cortisone and its derivates demonstrates influence to the metabolism of connective tissue. In this in vitro-study the action of water soluble Dexamethason (Schering) to corneal tissue is quantitatively determined. Incorporation of radioactive sulfate into the glycosaminoglycanes and the sulfate-hexosamine-quotient of keratansulfate and chondroitinsulfate is pointed out. 1. A 2 times 10-7 M Dexamethason-concentration and 6 hours incubation time causes reducing of sulfate incorporation in the case of keratansulfate (I) about 94 per cent and chondroitinsulfate (II) about 89 percent compared to nontreated control. Increasing concentration of Dexamethason leads the inhibition of sulfate incorporation to 66 per cent (I) and 63 per cent (II) respectively. Removing the epithelium from the stroma before incubation the Dexamethason concentration and 6 h incubation time only 84 percent and 80 per cent radioactive sulfate is found in keratansulfate and chondroitinsulfate. An increasing Dexamethason concentration leads to inhibition of 55 per cent (I) and 46 per cent (II) respectively. 2. A comparable inhibition of sulfate incorporation is demonstrated with constant Dexamethason concentration and variable duration of incubation. A 1 hour incubation reduced incorporation of sulfate to 89 per cent for keratansulfate and 81 per cent for chondroitinsulfate. The 24 hours incubation inhibits incorporation to 69 per cent (I) and 65 per cent (II) respectively.

Animals↗
PubMed1985

An acidic glycoprotein (100-K fucose-rich glycoprotein) from calf skin.

A new acidic glycoprotein was isolated from 4 M-guanidiunium chloride which had been extracted from neutral-salt-insoluble fractions of neonatal calf skin. During the process of purification, the glycoprotein co-migrated with proteodermatan sulphate and its sugar components mainly consisted of fucose, mannose and hexosamine. A broad band obtained by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis suggested that the molecular weight was 100,000. High-voltage electrophoresis, revealed acidic fragments in its tryptic peptides, while its oligosaccharide chains were shown to have on acidic nature by electrophoresis on a cellulose acetate membrane. These results show that the glycoprotein differs from other glycoproteins (fibronectin, laminin, entactin, nidogen and the 31-K protein of chondrocyte membrane) which have been reported in connective tissues.

Animals↗