Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Sialic Acids”

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 37 records · Page 2Linked to original sources
PubMed1998

O-acetylation of sialic acids.

Sialic acids can be acetylated at the 4, 7, 8 and/or 9 position. Biological roles of these substitutions have been missed until recently because of their low abundance and lability to conventional purification methods. The recent advances in the analysis of sialic acids have allowed to demonstrate that O-acetylation has a selective but widespread distribution. The metabolism of acetylated sialic acids is under the control of two groups of enzymes, O-acetyl transferases and 9-O-acetyl esterases. O-acetyl transferases are difficult to purify, and furthermore, attempts at expression cloning have failed in isolating the true 9-O-acetyl transferase cDNA. This explains that the regulation of the selective expression of O-acetylated sialic acid in not completely understood. Acetylation of sialic acid is expressed on the outer most part of the carbohydrate moiety of membrane and secreted glycoconjugates. This particular location explains why this modification is involved in cell/cell interactions and in the non-immune protection of mucosa.

Acetylation↗
PubMed2004

Characterization of the cellular uptake and metabolic conversion of acetylated N-acetylmannosamine (ManNAc) analogues to sialic acids.

"Sialic acid engineering" refers to the strategy where cell surface carbohydrates are modified by the biosynthetic incorporation of metabolic intermediates, such as non-natural N-acetylmannosamine (ManNAc) analogues, into cellular glycoconjugates. While this technology has promising research, biomedical, and biotechnological applications due to its ability to endow the cell surface with novel physical and chemical properties, its adoption on a large scale is hindered by the inefficient metabolic utilization of ManNAc analogues. We address this limitation by proposing the use of acetylated ManNAc analogues for sialic acid engineering applications. In this paper, the metabolic flux of these "second-generation" compounds into a cell, and, subsequently, into the target sialic acid biosynthetic pathway is characterized in detail. We show that acetylated ManNAc analogues are metabolized up to 900-fold more efficiently than their natural counterparts. The acetylated compounds, however, decrease cell viability under certain culture conditions. To determine if these toxic side effects can be avoided, we developed an assay to measure the cellular uptake of acetylated ManNAc from the culture medium and its subsequent flux into sialic acid biosynthetic pathway. This assay shows that the majority ( > 80%) of acetylated ManNAc is stored in a cellular "reservoir" capable of safely sequestering this analogue. These results provide conditions that, from a practical perspective, enable the acetylated analogues to be used safely and efficaciously and therefore offer a general strategy to facilitate metabolic substrate-based carbohydrate engineering efforts. In addition, these results provide fundamental new insights into the metabolic processing of non-natural monosaccharides.

Acetylation↗
PubMed1996

[Lipopolysaccharides containing sialic acid].

Sialic acids which are important constituents of animal tissue glycoconjugates are also present in antigens of some bacterial strains. Capsular polysaccharides with sialic acid have been extensively studied whereas little is known on lipopolysaccharides which contain sialic acid. The paper presents review of the data concerning structure of bacterial endotoxic lipopolysaccharides. Methodological peculiarities were described. Specially emphasized were endotoxins of Escherichia coli O24, O56, O104, Salmonella toucra O48, Citrobacter freundii O37 and Hafnia alvei strain PCM2386.

Bacterial Toxins↗
PubMedDate not supplied

An immobilized bienzyme system for assay of sialic acid.

Sialic acid has been assayed enzymatically by an immobilized two-enzyme system. The method includes cleavage of sialic acid to pyruvic acid by N-acetylneuraminic acid (NANA) aldolase and reduction of pyruvic acid by lactate dehydrogenase in the presence of NADH, which is followed photometrically at 349 nm. For the membrane preparation 5 units of lactate dehydrogenase and 1 unit of NANA-aldolase were used. The pH optimum of the reaction using potassium phosphate buffer was 7.0. This two-enzyme membrane remains 100% active for several weeks at 4 degrees C in the assay buffer and remains stable after performing experiments at 45 degrees C.

Animals↗
PubMed1978

Anti-inflammatory effect of sialic acid.

Sialic acid was shown to possess anti-inflammatory properties as measured by carrageenan-induced rat paw oedema and pleurisy tests. As the number of leukocytes mobilized was significantly reduced it was concluded that the inhibitory effect of sialic acid on leukocyte accumulation is responsible for the inhibition of exudate/oedema formation.

Animals↗
PubMed1986

Comparison of electron and chemical ionization mass spectrometry of sialic acids.

Sialic acids were analyzed as per-O-trimethylsilylated compounds by gas-liquid chromatography/mass spectrometry either on electron or chemical ionization by isobutane. Electron ionization mass spectra of these derivatives are very similar to those of the corresponding methyl esters described earlier whereas chemical ionization mass spectra are characterized in the high mass range by loss of the C-2 and the C-4 substituents from the M + 1 ion. Together with other fragment ions the seven different sialic acids analyzed could be clearly identified.

Esters↗
PubMed1998

Structure, function and metabolism of sialic acids.

Sialic acids represent a family of sugar molecules with an unusual and highly variable chemical structure that are found mostly in the terminal position of oligosaccharide chains on the surface of cells and molecules. These special features enable them to fulfil several important and even diametrical biological functions. Because of the great importance of sialic acids, it is also worth having a look at their metabolism in order to get an idea of the intimate connection between structure and function of these fascinating molecules and the often serious consequences that results from disturbances in the balance of metabolic reactions. The latter can be due to genetic disorders that result in the absence of certain enzyme activity, leading to severe illness or even to death.

Animals↗
PubMed1997

Serum alpha 1-acid glycoprotein, sialic acid, and protein binding of disopyramide in normal subjects and cardiac patients.

AIM: To study influence of congestive heart failure (CHF) and acute myocardial infarction (AMI) on alpha 1-acid glycoprotein (AGP) and sialic acid (SA) concentration, and binding of AGP to disopyramide (Dis). METHODS: Sera from 85 healthy subjects, 6 patients with CHF, and 6 patients with AMI were determined by immunochemistry for AGP, by HPLC method for sialic acid (SA), and by ultrafiltration and HPLC for the free fraction of Dis. RESULTS: Serum AGP concentrations (g.L-1) were 0.74 +/- 0.16 (healthy), 1.18 +/- 0.40 (d 1, CHF) and 0.90 +/- 0.24 (d 14, CHF), 1.53 +/- 0.26 (d 5, AMI) and 1.08 (d 14, AMI). The free Dis were 1.76 +/- 0.62 (d 1) and 2.14 +/- 0.48 (d 14), in CHF patients, 1.66 +/- 0.52 (d 5) and 1.77 (d 14) in AMI patients. The changes of serum SA and AGP concentrations showed the same tendency. CONCLUSION: The free Dis in serum was affected by the change of AGP binding in CHF and AMI patients.

Adult↗
PubMed1980

Effect of corticosteroids on intraocular pressure, ascorbic acid and sialic acid concentrations in aqueous humour and on mucopolysaccharides biosynthesis in the cornea of rabbits.

The effect of daily oral administration of corticosteroids on ocular dynamics and biosynthesis of corneal mucopolysaccharides was investigated using rabbits as experimental animals. Fluocortolone treatment at doses of 0.05 to 10 mg/kg resulted in a dose-dependent rise of intraocular pressure (IOP). At higher dose levels of 5 and 10 mg fluocortolonel kg daily over 14 days, an inhibition of 35S-incorporation and a reduction in the nexosamine content of the corneal mucopolysaccharides was observed. When the effects of prednisolone, fluocortolone and dexamethasone on IOP were compared the relative order of the potency for the corticosteroids was as follows: dexamethasone > fluocortolone > prednisolone. The influence of different doses of fluocortolone on ascorbic and sialic acid content in aqueous humour and plasma was also studied. Levels of 5 and 10 mg/kg caused a significant reduction of ascorbic acid and a slight increase in sialic acid content in aqueous humor besides an elevation of IOP, whereas the plasma levels of both components did not reveal any difference from control group. These findings suggest that the blood-aqueous barrier becomes more permeable under the treatment with corticosteroids, especially in doses which are known to be toxic in animals. Further, the rabbit can be used as an experimental animal for comparing the effets of different corticosteroids on IOP.

Animals↗
PubMed1988

Sialic acid as a marker for differentiation between benign and malignant intracranial tumors.

One of the characteristics of malignant tumor cells is the production of glycocompounds with a high content of N-acetylneuraminic acid (sialic acid). Total sialic acid concentration was determined in the serum of 136 patients with an intracranial tumor. The concentration was determined enzymatically and using HPLC. Both methods had a relatively high specificity (90%), provided an inflammatory process due to an infection could be excluded. Sensitivity was 72.6%; the cut-off level of sialic acid concentration was determined to be 2.75 mumol/ml. There was a significant difference in the average sialic acid concentration of benign and malignant tumors. The test was least reliable in determining whether the growth of an astrocytoma is malignant.

Adolescent↗
PubMed1991

Serum sialic acid, fucose, sialic acid/fucose ratio as tumor markers in oral cancer.

To our knowledge, no study has been undertaken before by any researcher as to the direction of content of the components of serum glycoproteins simultaneously as well as their ratios in oral cancer patients. The aim of the present paper is to establish the direct relationship between fucose and sialic acid levels in the sera of such patients. The biochemical levels were studied among 37 oral cancer patients and were compared with 15 controls.

Biomarkers, Tumor↗
PubMed1983

Developmental changes of hematoside of rat small intestine. Postnatal hydroxylation of fatty acids and sialic acid.

The hematoside of rat intestine is analyzed from 1 day to 60 days of age. During the first 3 weeks of life, GM3 (N-acetylneuraminylgalactosylglucosylceramide) contains only nonhydroxylated fatty acids and accounts for 80-90% of the ganglioside sialic acid. Its concentration is maximum at 6 days (315 micrograms of NeuAc/g of intestine) and falls abruptly over the next 2 weeks. It reaches 45 micrograms of NeuAc/g of intestine at 60 days. Between 28 and 60 days, GM3 accounts for 72% of the total intestinal gangliosides. From 21 days on, structural modifications of GM3 are observed. N-Acetylneuraminic acid is replaced progressively by N-glycolylneuraminic acid and nonhydroxylated fatty acids are replaced by alpha-hydroxylated fatty acids. Both changes are interpreted as the result of hydroxylations of GM3 components which are triggered at the time of weaning. These hydroxylations take place chiefly in epithelial cells and to a much lesser extent in nonepithelial residue, as shown by the separate analysis of both compartments of rat intestine at 38 and 60 days. In epithelial cells, the highest percentage of alpha-hydroxylated fatty acids and of N-glycolylneuraminic acid is found at 60 days. In addition, 4 D-hydroxysphinganine is the major base of the GM3 of intestinal cells from birth to adulthood.

Aging↗
PubMed1986

Studies of lysosomal sialic acid metabolism: retention of sialic acid by Salla disease lysosomes.

Purified rat liver lysosomes were incubated in 0.2 M sialic acid resulting in an increase in lysosomal free sialic acid of 3.8 +/- 1.5 nmol/unit beta hexosaminidase. Sialic acid loss by these lysosomes was stimulated 2-3 fold by 25 mM sodium phosphate. Loss of sialic acid by lysosomes from cultured human diploid fibroblasts was similar to that observed in rat liver lysosomes while loss of sialic acid by lysosomes from cultured fibroblasts from a patient with infantile Salla disease occurred much more slowly. Salla disease appears to be the consequence of defective lysosomal transport of sialic acid and is analogous to cystinosis, a disorder of lysosomal amino acid transport.

Animals↗
PubMed1976

Cytidine-5'-monophosphate-N-acetylneuraminic acid. Asialoglycoprotein sialic acid transferase activity in liver and serum of patients with juvenile hepatic cirrhosis and alpha-1-antitrypsin deficiency.

The molecular basis for the accumulation of a substance which displays the immunological reactivity of alpha-1-antitrypsin within vesicles of liver parenchymal cells of individuals with hepatic cirrhosis and serum alpha-1-antitrypsin deficiency remains unclear. We recently reported that serum from a patient with alpha-1-antitrypsin deficiency and hepatic cirrhosis was substantially deficient in sialyltransferease (EC 2.4.99.1) an enzyme which transfers sialic acid from cytidine 5'-monophosphate-N-acetylneuraminic acid to a variety of asialoglycoprotein acceptors. In the present report we have extended these studies to include serum from five additional patients with alpha-1-antitrypsin deficiency and juvenile hepatic cirrhosis as well as a liver specimen obtained at autopsy of one of these patients. We find the sialytransferase activity in serum from six patients with alpha-1-antitrypsin deficiency and hepatic cirrhosis to be 50% of healthy pediatric control values and 30% of pediatric patients with liver disease. However, serum from family members homozygous for alpha-1-antitrypsin deficiency but without hepatic cirrhosis, and serum from patients with a variety of other kinds of liver disease, failed to exhibit the marked sialytransferase deficiency. Similar assays carried out on a homogenate of a liver sample from one patient with alpha-1-antitrypsin deficiency and hepatic cirrhosis indicated that the deficiency of sialyltransferase activity was not demonstrable in liver. Furthermore, a comparative kinetic analysis of serum and liver sialytransferase in normal and afflicted individuals failed to detect differences in substrate affinities which might account for a decrease in functional sialyltransferase capacity in individuals with alpha-1-antitrypsin deficiency and hepatic cirrhosis. These observations suggest that the serum sialyltransferase deficiency in such patients probably arises after chronic and extensive liver disease involving hepatic accumulation of alpha-1-antitrypsin rather than the enzyme deficiency being the primary cause of the hepatic cirrhosis and alpha-1-antitrypsin deficiency.

Adolescent↗
PubMed2001

Versatile biosynthetic engineering of sialic acid in living cells using synthetic sialic acid analogues.

Sialic acids are critical components of many glycoconjugates involved in biologically important ligand-receptor interactions. Quantitative and structural variations of sialic acid residues can profoundly affect specific cell-cell, pathogen-cell, or drug-cell interactions, but manipulation of sialic acids in mammalian cells has been technically limited. We describe the finding of a previously unrecognized and efficient uptake and incorporation of sialic acid analogues in mammalian cells. We added 16 synthetic sialic acid analogues carrying distinct C-1, C-5, or C-9 substitutions individually to cell cultures of which 10 were readily taken up and incorporated. Uptake of C-5- and C-9-substituted sialic acids resulted in the structural modification of up to 95% of sialic acids on the cell surface. Functionally, binding of murine sialic acid-binding immunoglobulin-like lectin-2 (Siglec-2, CD22) to cells increased after N-glycolylneuraminic acid treatment, whereas 9-iodo-N-acetylneuraminic acid abolished binding. Furthermore, susceptibility to infection by the B-lymphotropic papovavirus via a sialylated receptor was markedly enhanced following pretreatment of host cells with selected sialic acid analogues including 9-iodo-N-acetylneuraminic acid. This novel experimental strategy allows for an efficient biosynthetic engineering of surface sialylation in living cells. It is versatile, extending the repertoire of modification sites at least to C-9 and enables detailed structure-function studies of sialic acid-dependent ligand-receptor interactions in their native context.

Animals↗
PubMed1987

Prenatal detection of Salla disease based upon increased free sialic acid in amniocytes.

Salla disease is an autosomal recessive lysosomal storage disease relatively common in the Finnish population. The main manifestations of more than 70 patients detected to date are severe psychomotor retardation and ataxia of early onset. Intracellular free N-acetylneuraminic acid (sialic acid) is increased 10-20-fold and localized in the lysosomes. Four pregnancies at risk were monitored by quantitation of free and total sialic acid in amniocytes and supernatant amniotic fluid by high-performance liquid chromatography. In 3 children results were normal. Free sialic acid content of the amniocytes from one affected child was 2.6 nmol/mg protein, which was approximately 5 times higher than that of the 3 unaffected children (0.3 to 0.8) and 14 control samples (0.3 to 0.9). The ratio of free/total sialic acid of the amniocytes also clearly distinguished the affected pregnancy (13.8%) from the unaffected (2.3-4.8%) and control individuals (1.8-5.3%). This represents the first successful prenatal identification of a patient with Salla disease and indicates that both free sialic acid and free/total sialic acid ratio should be monitored in pregnancies at risk for the disease.

Amniocentesis↗