Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HEXOSAMINES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources
PubMed2006

Biofilm matrix of Candida albicans and Candida tropicalis: chemical composition and role in drug resistance.

Matrix material was extracted from biofilms of Candida albicans and Candida tropicalis and analysed chemically. Both preparations contained carbohydrate, protein, hexosamine, phosphorus and uronic acid. However, the major component in C. albicans matrix was glucose (32%), whereas in C. tropicalis matrix it was hexosamine (27%). Biofilms of C. albicans were more easily detached from plastic surfaces by treatment with the enzyme lyticase (beta-1,3-glucanase) than were those of C. tropicalis. Biofilms of C. albicans were also partially detached by treatment with proteinase K, chitinase, DNase I, or beta-N-acetylglucosaminidase, whereas C. tropicalis biofilms were only affected by lipase type VII or chitinase. To investigate a possible role for the matrix in biofilm resistance to antifungal agents, biofilms of C. albicans were grown under conditions of continuous flow in a modified Robbins device (MRD). These biofilms produced more matrix material than those grown statically, and were significantly more resistant to amphotericin B. Biofilms of C. tropicalis synthesized large amounts of matrix material even when grown statically, and such biofilms were completely resistant to both amphotericin B and fluconazole. Mixed-species biofilms of C. albicans and a slime-producing strain of Staphylococcus epidermidis (RP62A), when grown statically or in the MRD, were also completely resistant to amphotericin B and fluconazole. Mixed-species biofilms of C. albicans and a slime-negative mutant of S. epidermidis (M7), on the other hand, were completely drug resistant only when grown under flow conditions. These results demonstrate that the matrix can make a significant contribution to drug resistance in Candida biofilms, especially under conditions similar to those found in catheter infections in vivo, and that the composition of the matrix material is an important determinant in resistance.

Amphotericin B↗
PubMed2005

Relationship between protein O-linked glycosylation and insulin-stimulated glucose transport in rat skeletal muscle following calorie restriction or exposure to O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate.

AIMS AND BACKGROUND: Protein O-linked glycosylation is regulated in vivo by the concentration of hexosamine substrates. Calorie restriction (60% of ad libitum intake) for 20 days causes decreased UDP-N-acetylhexosamine levels and increased insulin-mediated glucose transport in rat skeletal muscle. Conversely, prolonged incubation (19 h) of muscle with O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenyl-carbamate (PUGNAc; an inhibitor of N-acetyl-beta-D-glucosaminidase) is characterized by increased O-linked glycosylation and insulin resistance. We aimed to determine the calorie restriction effect on O-linked glycosylation and characterize the temporal relationship between PUGNAc-induced O-linked glycosylation and insulin resistance. HYPOTHESIS: A calorie restriction protocol characterized by decreased muscle hexosamine levels will result in a global reduction in O-linked glycosylated proteins in muscle, and PUGNAc-induced insulin resistance will coincide with increased O-linked glycosylation. METHODS: Plantaris muscle and liver from rats (ad libitum or calorie restricted) were analysed for O-linked glycosylation using two antibodies against different O-linked N-acetylglucosamine epitopes. Also, rat epitrochlearis muscles were incubated for 8.5 h +/- 100 mum PUGNAc prior to measurement of [(3)H]-3-O-methylglucose transport and O-linked glycosylation. RESULTS: Calorie restriction did not alter protein O-linked glycosylated levels in muscle or liver. Incubation with PUGNAc for 8.5 h resulted in increased in O-linked glycosylation but unaltered basal or insulin-stimulated glucose transport. CONCLUSIONS: The delay between O-linked glycosylation and insulin resistance in muscle incubated with PUGNAc suggests an indirect, relatively slow mechanism for insulin resistance. The effect of calorie restriction on insulin action in muscle is unlikely to be the direct result of a global change in protein O-linked glycosylation.

Acetylglucosamine↗
PubMed2005

Review article: diabetes and atherosclerosis--running on a common road.

Insulin resistance accounts for glucotoxicity observed in diabetes and atherosclerotic disease. Glucotoxicity depends from the shift of glucose metabolism from the glycolytic pathway to minor forms of glucose metabolism, including sorbitol, hexosamine and AGE pathways. These pathways increase oxidative stress and/or block insulin signalling so leading to a further decline of insulin action. A genetic defect of insulin action (the g972R Insulin Receptor Substrate 1 variant) may sustain endothelial dysfunction, the first defect of vascular homeostasis in the road to atherosclerosis. Furthermore, hyperglycemia even in the absence of insulin resistance, activates the hexosamine pathway in endothelial cells, affects the production of nitric oxide, increases the production and activity of metalloproteinase 2 and 9 and activates endothelium thus provoking endothelial dysfunction. Oxidative stress and inflammation through activtion of IKK-beta could determine insulin resistance impairing IRS-1 ability to activate the metabolic branch of insulin signalling. Furthermore, increased oxidative stress may be speculated to affect glucose metabolism in a proportion of patients with coronary artery disease. In conclusion, type 2 diabetes and atherosclerosis share vascular homeostasis and glucose metabolism and insulin resistance might be the common road where diabetes and atherosclerosis run together.

Atherosclerosis↗
PubMed1995

Glucosamine 6-phosphate deaminase in normal human erythrocytes.

In the course of an investigation of hexosamine catabolism in the human malaria parasite, Plasmodium falciparum, it became apparent that a basic understanding of the relevant enzymatic reactions in the host erythrocyte is lacking. To acquire the necessary basic knowledge, we have determined the activities of several enzymes involved in hexosamine metabolism in normal human red blood cells. In the present communication we report the results of studies of glucosamine 6-phosphate deaminase (GlcN6-P) using a newly developed sensitive radiometric assay. The mean specific activity in extracts of fresh erythrocytes assayed within 4h of collection was 14.7 nmol/h/mg protein, whereas preparations from older erythrocytes that had been stored at 4 degrees C for up to 4 weeks had a mean specific activity of 6.2 nmol/h/mg. Characterization of the deaminase by chromatofocusing gave a pI of 8.55. The enzyme was optimally active at pH 9.0 and had a Km of 41 microM. The metal chelators EDTA and EGTA were non-inhibitory; however, inhibition was observed in the presence of metal ions, especially Cu2+, Ni2+ and Zn2+. In addition, the deaminase was also inhibited by several sugar phosphates including the reaction product, fructose 6-phosphate.

Aldose-Ketose Isomerases↗
PubMed1980

An antigen common to a wide range of bacteria. 2. A biochemical study of a "common antigen" from Pseudomonas aeruginosa.

Common Antigen (CA) of Pseudomonas aeruginosa has been shown to be a protein composed of polypeptide subunits of a molecular weight (MW) of about 62 000. The MW of this protein was estimated to 665 000 by gel filtration on sepharose CL-6B, to 800 000 by electrophoresis on polyacrylamide gradient gels and to about 900 000 by ultracentrifugation, on a sucrose gradient. By analytical ultracentrifugation with Schlieren optics a sedimentation coefficient (S20 degrees, W) of 22.65 was calculated. The isoelectrical point was determined to pH 4.4. The antigen was decomposed on exposure to proteolytic enzymes. Polysaccharide, lipid, deoxyribonucleic acid or ribonucleic acid were not demonstrated in CA. The amino acid content of CA was determined, and no hexosamine or abnormal residues were observed. The amino acid content of CA was determined, and no hexosamine or abnormal residues were observed. The antigen was degraded when heated to 100 degrees C for 4 min or when exposed to pH below 4 or above 11 at 4 degree C. CA has been isolated from the cytoplasmic water-soluble fraction of disintegrated bacteria and only trace-amounts could be obtained from envelope fractions after solubilization with Triton X-100.

Amino Acids↗
PubMed1999

Nutrient modulation of cellular insulin action.

Abundant evidence supports a crucial role for dietary factors in the induction and maintenance of insulin resistance. At the cellular and tissue level, the availability of substrates for cellular energy production may play an important role in metabolic regulation and, in particular, in determining the response to insulin stimulation. The infusion of amino acids or fatty acids decreases insulin-stimulated glucose disposal in vivo; sustained hyperglycemia also induces insulin resistance. To determine whether nutrients directly affect insulin signaling, we have evaluated the impact of fatty acids, amino acids, and activation of the hexosamine pathway on insulin signaling in both cultured cells and animal models. We demonstrate that fatty acids and amino acids inhibit early post-receptor steps in insulin action, including tyrosine phosphorylation of insulin receptor substrate (IRS) proteins and activation of phosphatidylinositol 3-kinase (PI3-kinase), both in vitro and in several in vivo models. Similarly, activation of the hexosamine pathway by infusion of glucosamine also reduces insulin-stimulated phosphorylation of IRS proteins, activation of PI3-kinase, and activation of glycogen synthase. These data suggest that nutrients directly modulate insulin signaling, perhaps via common pathways, and thus contribute to cellular insulin resistance.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Enhanced expression of osteopontin by high glucose. Involvement of osteopontin in diabetic macroangiopathy.

Atherosclerotic vascular disease is a major complication of diabetic patients. Osteopontin has recently been implicated in the development of atherosclerosis. In the present study, we have investigated the effects of high glucose on expression of osteopontin in cultured rat aortic smooth muscle cells. High concentrations of glucose increased osteopontin secretion from the cells, and the increased secretion was completely inhibited by an inhibitor of protein kinase C, GF109203X. Northern blot analysis confirmed the enhanced effect of glucose on expression of osteopontin mRNA. Promoter activity of osteopontin, measured using the osteopontin promoter/luciferase expression vector system, was increased by high glucose, and the enhanced effect was completely inhibited by GF109203X. Glucosamine also increased the promoter activity of osteopontin. Azaserine, an inhibitor of glutamine:fructose-6-phosphate amidotransferase, the key enzyme of the hexosamine pathway, profoundly inhibited high glucose-mediated increase in the promoter activity. Taken together, these data indicate that high glucose enhances the expression of osteopontin at the transcriptional level possibly through the activation of protein kinase C as well as the hexosamine pathway. Our results suggest that osteopontin could play a role in the development of diabetic vascular complications.

Animals↗
PubMed1987

Physical heterogeneity of neisserial lipooligosaccharides reflects oligosaccharides that differ in apparent molecular weight, chemical composition, and antigenic expression.

We studied the oligosaccharides (OS) of outer membrane lipooligosaccharides (LOS) of Neisseria gonorrhoeae and Neisseria meningitidis. OS from the LOS of an individual neisserial strain always eluted from Sephadex G-50S as multiple peaks; the polyacrylamide gel elution profiles were nearly identical to the polyacrylamide gel electrophoresis profiles of the sodium dodecyl sulfate-disaggregated native LOS from which the OS were derived. Neisserial OS coeluted with Dex14 to Dex27 dextran oligomers (Mr, 2,210 to 4,320). Monosaccharide composition varied among the several OS released from the LOS of a single strain. The two OS of a gonococcal strain sensitive to normal human serum (NHS) bacteriolysis (sers) varied in their ability to inhibit the binding of NHS immunoglobulin M to their parental LOS. The OS that was rich in hexosamines inhibited NHS immune lysis of its parent strain; the OS that was poor in hexosamines did not. We conclude that structural differences in their OS account for the Mr heterogeneity of the LOS of a strain.

Acetates↗
PubMed1998

Structural properties of lipopolysaccharides from Rickettsia typhi and Rickettsia prowazekii and their chemical similarity to the lipopolysaccharide from Proteus vulgaris OX19 used in the Weil-Felix test.

The lipopolysaccharides (LPSs) isolated from typhus group (TG) rickettsiae Rickettsia typhi and Rickettsia prowazekii were characterized by chemical analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by silver staining. LPSs from two species of TG rickettsiae contained glucose, 3-deoxy-D-manno-octulosonic acid, glucosamine, quinovosamine, phosphate, and fatty acids (beta-hydroxylmyristic acid and heneicosanoic acid) but not heptose. The O-polysaccharides of these LPSs were composed of glucose, glucosamine, quinovosamine, and phosphorylated hexosamine. Resolution of these LPSs by their apparent molecular masses by SDS-PAGE showed that they have a common ladder-like pattern. Based on the results of chemical composition and SDS-PAGE pattern, we suggest that these LPSs act as group-specific antigens. Furthermore, glucosamine, quinovosamine, and phosphorylated hexosamine were also found in the O-polysaccharide of the LPS from Proteus vulgaris OX19 used in the Weil-Felix test, suggesting that they may represent the antigens common to LPSs from TG rickettsiae and P. vulgaris OX19.

Antigens, Bacterial↗
PubMed1970

Separation and localization of cell wall layers of a gram-negative bacterium.

The cell envelope of a marine pseudomonad as seen in thin section by electron microscopy has the double-membrane structure typical of other gram-negative bacteria. Cells washed with a solution containing Na(+), K(+), and Mg(++) at their concentrations in the growth medium, when suspended briefly in 0.5 m sucrose, lost 13% of their hexosamine in a form nonsedimentable by centrifugation at 73,000 x g. Since the resulting cells in thin section appeared unchanged, it was concluded that the material released was derived from a nonstaining, loosely bound outer layer. This same layer could be removed from the cells by washing with 0.5 m NaCl. A second nonsedimentable fraction was released after successive suspension of the cells in 0.5 m sucrose. Since this material was released only when the outer double-track structure had broken, it was concluded that it arose from a layer immediately underlying the latter layer. The three layers differed in their content of hexosamine and protein. None of the layers released contained muramic or diaminopimelic acid. The cell form remaining was rod shaped and appeared in thin section to be bounded only by its cytoplasmic membrane. This form contained all the muramic and diaminopimelic acid in the cell. Treatment with lysozyme released the muramic and diaminopimelic acid and converted the rod form to a protoplast, indicating that in the rod form (mureinoplast) a thin layer of peptidoglycan is located on the outside surface of the cytoplasmic membrane. Thus, five separate layers have been detected in the cell envelope of this marine pseudomonad.

Journal Article↗
PubMed1970

Quantitation, chemical characteristics, and ultrastructure of the three outer cell wall layers of a gram-negative bacterium.

The cell wall of the gram-negative marine pseudomonad (American Type Culture Collection 19855) consists of three layers: the loosely bound outer layer, the outer double-track layer, and the underlying layer. These three layers constitute 4.7, 7.9, and 6.1%, respectively, of the dry weight of the whole cells. All three layers contained protein, lipid, and carbohydrate. The loosely bound outer layer and underlying layer were lower in protein and lipid and higher in amino and nonamino carbohydrate than the outer double-track layer. All three layers contained proteins with similar amino acid compositions. Minicell-like forms attached to the ends of cells were separated with and fractionated from the units of loosely bound outer layer. Examination of negatively stained preparations by electron microscopy revealed the loosely bound outer layer to be composed largely of units ranging from 400 to 1000 nm in diameter. The outer double-track layer, by the same technique, appeared as large, usually rounded sheets, each with a distinct rim. Washing this layer changed the gross chemical composition but did not affect the bimolecular leaflet appearance in thin sections. The underlying layer, when negatively stained, appeared to be composed of a heterogeneous mixture of particles differing in size and shape. It was separated by gel filtration into a large fraction with a molecular weight range in excess of 20 x 10(6) to 40 x 10(6) and a small fraction with a lower range of molecular weight. The larger fraction contained both protein and hexosamine, whereas the smaller one contained protein and only traces of hexosamine. A cytochrome-like pigment separated with this latter fraction.

Journal Article↗
PubMed1981

Incorporation of substrate cell lipid A components into the lipopolysaccharide of intraperiplasmically grown Bdellovibrio bacteriovorus.

The composition of Bdellovibrio bacteriovorus lipopolysaccharide (LPS) was determined for cells grown axenically and intraperiplasmically on Escherichia coli or Pseudomonas putida. The LPS of axenically grown bdellovibrios contained glucose and fucosamine as the only detectable neutral sugar and amino sugar, and nonadecenoic acid (19:1) as the predominant fatty acid. Additional fatty acids, heptose, ketodeoxyoctoic acid, and phosphate were also detected. LPS from bdellovibrios grown intraperiplasmically contained components characteristic of both axenically grown bdellovibrios and the substrate cells. Substrate cell-derived LPS fatty acids made up the majority of the bdellovibrio LPS fatty acids and were present in about the same proportions as in the substrate cell LPS. Glucosamine derived from E. coli LPS amounted to about one-third of the hexosamine residues in intraperiplasmically grown bdellovibrio LPS. However, galactose, characteristic of the E. coli outer core and O antigen, was not detected in the bdellovibrio LPS, suggesting that only lipid A components of the substrate cell were incorporated. Substrate cell-derived and bdellovibrio-synthesized LPS materials were conserved in the B. bacteriovorus outer membrane for at least two cycles of intraperiplasmic growth. When bdellovibrios were grown on two different substrate cells successively, lipid A components were taken up from the second while the components incorporated from the lipid A of the first were conserved in the bdellovibrio LPS. The data show that substrate cell lipid A components were incorporated into B. bacteriovorus lipid A during intraperiplasmic growth with little or no change, and that these components, fatty acids and hexosamines, comprised a substantial portion of bdellovibrio lipid A.

Bdellovibrio↗
PubMed1965

STUDIES OF STREPTOCOCCAL CELL WALLS. VII. CARBOHYDRATE COMPOSITION OF GROUP B CELL WALLS.

Wittner, Masako K. (Presbyterian-St. Luke's Hospital, Chicago, Ill.), and James A. Hayashi. Studies of streptococcal cell walls. VII. Carbohydrate composition of group B cell walls. J. Bacteriol. 89:398-402. 1965.-Group B streptococcal cell walls contain 63% protein, 10% rhamnose, 18% hexose (mainly galactose, but also some glucose), 7% hexosamine (mainly glucosamine, but also galactosamine), and 3% muramic acid. The group and type antigens were extracted from isolated cell walls by acid treatment and enzymatic hydrolysis, and fractionated either with ethanol or on a diethylaminoethyl-cellulose column. Serological and chemical analyses of the fractions obtained in the two fractionation methods show that the group antigen is a rhamnose-rich polysaccharide and that the type antigen is rich in galactose and contains hexosamines.

Antigens↗
PubMed1967

Sphere-rod morphogenesis in Arthrobacter crystallopoietes. I. Cell wall composition and polysaccharides of the peptidoglycan.

Cell walls of Arthrobacter crystallopoietes were prepared from cells grown as spheres and from peptone- and succinate-induced rod stage cells. Undegraded polysaccharide backbones of the peptidoglycans were isolated from myxobacter AL-1 protease digests by ECTEOLA cellulose and Sephadex G-50 chromatography. The polysaccharide backbones of the sphere cell wall peptidoglycan are heterogeneous in their size, and average less than 40 hexosamines per chain. Those of the rod cell walls are homogeneous in size and average 114 to 135 hexosamines per chain.

Amino Acids↗
PubMed1968

Isolation and chemical structure of the peptidoglycan of Spirillum serpens cell walls.

The peptidoglycan layer of Spirillum serpens cell walls was isolated from intact cells after treatment with sodium dodecylsulfate and digestion with Pronase. The isolated peptidoglycan contained glucosamine, muramic acid, alanine, glutamic acid, and meso-diaminopimelic acid in the approximate molar ratio of 1:1:2:1:1. Aspartic acid and glycine were the only other amino acids found in significant quantities. N-terminal amino acid analyses of the tetrapeptide amino acids in the peptidoglycan revealed that 54% of the diaminopimelic acid molecules are involved in cross-linkage between tetrapeptides. This amount of cross-linkage is greater than that found in the peptidoglycan of previously studied cell walls of gram-negative bacteria. The polysaccharide backbone was isolated, after myxobacter AL-1 enzyme digestion of the peptidoglycan, by fractionation with ECTEOLA-cellulose and Sephadex G-100. An average length of 99 hexosamines for the polysaccharide chains was found (ratio of total hexosamines to reducing end groups).

Amino Acids↗
PubMed2005

Structural and functional modification of THP on nitration: comparison with stone formers THP.

OBJECTIVE: The crucial steps involved in the lithogenic process are governed by the macromolecular components of urine, of which proteins play a major role. Structurally abnormal proteins have been reported to be present in the urine of stone formers. Free radical injury has come a long way in explaining some of the pathophysiological events of renal lithiasis. Thus, our present work was designed to study the impact of the potent oxidant peroxynitrite on the biochemical components of the urinary Tamm-Horsfall glycoprotein (THP). MATERIALS AND METHODS: Nitration on THP was carried out using peroxynitrite (ONOO(-)). After nitration, biochemical components like thiols, S-nitrosothiol, hexose, hexosamine and sialic acid were determined and these factors were compared with those of stone formers and normal THP. Crystallization behavior of control, nitrated NS-THP and stone formers THP was studied. RESULTS: There was a significant decrease in thiol, hexose, hexosamine and sialic acid contents in stone formers and nitrated NS-THP, when compared to that of the control THP. In contrast to this, S-nitrosothiol content was significantly increased in stone formers and nitrated NS-THP (p < 0.001) when compared with the control THP. NO(x) metabolites were significantly elevated in stone formers THP when compared with that of control THP. When subjected to CaOx crystallization, stone formers THP and nitrated NS-THP promoted both CaOx nucleation and aggregation, while normal THP was found to be an inhibitor of the above processes. CONCLUSION: From our results we conclude that nitration of THP could represent one of the prime events in modifying kinetic behavior of THP, thus converting THP into a heterogeneous nucleator of renal calculi formation.

Crystallization↗
PubMed1988

Prenatal protein-energy malnutrition alters various biochemical components of the membranous bones in fetal rats.

The effects of prenatal protein-energy malnutrition on the biochemical parameters of the membranous bone were studied using fetal rats. Timed pregnant rats were fed a protein-deficient diet as an experimental group from day 13 of gestation, whereas control dams were fed a normal protein diet. By day 15, radioactive Na2SO4 was injected. On day 22, all fetuses were delivered by cesarean section. The hexosamine content per milligram dry tissue, and the protein and hexosamine contents per guanidine-HCl extract were greater in the mandibles but less in the calvaria of the malnourished group than in those of the controls. Calcium content per gram dry tissue was lower in both bones of the malnourished group. 35S-sulfate uptake per milligram dry tissue or milligram proteoglycan was greater in the malnourished group than in the controls in both bones. The mandible in the malnourished group had less lower-weight molecular proteoglycan subunits in the dissociative condition. Protein-energy malnutrition affects the mandible and calvaria in different ways, although both bones originate from membranous bone. Insufficient degradation of proteoglycan could be the reason for the delay of mineralization in the malnourished bones.

Animals↗
PubMed2003

High glucose-induced upregulation of osteopontin is mediated via Rho/Rho kinase pathway in cultured rat aortic smooth muscle cells.

OBJECTIVE: Osteopontin is upregulated in the diabetic vascular wall and in vascular smooth muscle cells cultured under high glucose concentration. In the present study, we analyzed the mechanism of high glucose-induced upregulation of osteopontin in cultured rat aortic smooth muscle cells. METHODS AND RESULTS: We found that an inhibitor of Rho-associated protein kinase, Y-27632, suppressed osteopontin mRNA expression under high glucose concentration. Transfection of cells with a constitutive active Rho mutant, pSRalpha-myc-RhoDA, enhanced osteopontin mRNA expression. Furthermore, incubation of cells under high glucose concentration activated Rho, indicating that Rho/Rho kinase pathway mediates high-glucose-stimulated osteopontin expression. Treatment of cells with an inhibitor of protein kinase C, GF109203X, and azaserine, an inhibitor of the hexosamine pathway, suppressed high glucose-induced Rho activation. Glucosamine treatment was shown to activate Rho. Treatment of cells with an inhibitor of MEK1, PD98059, suppressed osteopontin mRNA expression under high glucose concentration. Incubation of cells under high glucose concentration activated ERK. Finally, transfection of cells with pSRalpha-myc-RhoDA also activated ERK. CONCLUSIONS: In conclusion, our present findings support a notion that Rho/Rho kinase pathway functions downstream of protein kinase C and the hexosamine pathways and upstream of ERK in mediating high-glucose-induced upregulation of osteopontin expression.

Amides↗