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Biomedical subjects

R Schauer

Publications and source records attributed to R Schauer.

At least 181 records · Page 10Linked to original sources
PubMed1986

Properties of human liver lysosomal sialidase.

Sialidase in human liver was localized predominantly in the lysosomal fraction. Microsomal and nuclear fractions contained some activity but no cytosolic enzyme could be detected. The lysosomal enzyme fraction is active with gangliosides, fetuin, mucus glycoprotein, sialyllactose and other sialyloligosaccharides. The preferred rate of enzymic hydrolysis of sialyl linkages is alpha(2-3) greater than alpha(2-6) greater than alpha(2-8) and this is governed by the Vmax values, as Km values were similar for all substrates tested. N-Acetyl-neuraminic acid is released faster than N-glycoloylneuraminic acid. Using the inhibitors N-acetyl-2-deoxy-2,3-didehydroneuraminic acid and N-(4-nitrophenyl)oxamic acid with selected substrates the existence of at least two types of sialidase activity could be demonstrated. One is active preferentially with gangliosides and sialyllactose and the other with fetuin and sialyhexasaccharides. Strong inhibition by Cu2+ and Hg2+ was found with ganglioside and sialyllactose as substrates. The presence of a sialate O-acetylesterase acting on hematoside containing N-glycoloyl-4-O-acetylneuraminic acid was established.

Enzyme Stability↗
PubMed1986

The galactose-recognizing system of rat peritoneal macrophages. Receptor-mediated binding and uptake of glycoproteins.

Binding and phagocytosis of sialidase-treated cells by peritoneal macrophages is mediated by a galactose-specific receptor. So far, only cells or particles exposing terminal galactose residues were demonstrated to be ligands. We present results obtained with a newly developed radio-receptor assay, which proves both binding and uptake of glycoproteins mediated by the galactose-recognizing receptor of peritoneal macrophages. Requirement of Ca2+ for binding is used to distinguish between reversibly surface-bound and irreversibly internalized ligands. By using this approach, the uptake of the ligand is followed and its inhibition with phenylglyoxal and N-ethylmaleimide is demonstrated. Evidence was also obtained that internalization is followed by degradation of the ligand. Studies on the specificity show that only galactose is recognized but that the binding strength depends on the arrangement of galactose residues presented by the ligand.

Animals↗
PubMed1985

Structural parameters and natural occurrence of 2-deoxy-2,3-didehydro-N-glycoloylneuraminic acid.

2-Deoxy-2,3-didehydro-N-glycoloylneuraminic acid has been found to occur in porcine, bovine and equine submandibular glands as well as in the urine of pig, horse and rat. This novel, unsaturated sialic acid was isolated by gel filtration and ion-exchange chromatography. Final purification was achieved by column chromatography or by preparative thin-layer chromatography on cellulose. The structural analysis was performed by combined capillary gas-liquid chromatography/mass spectrometry. The various data were compared with those from synthetic 2-deoxy-2,3-didehydro-N-glycoloylneuraminic acid. Besides of the unsaturated N-glycoloylated sialic acid, also the corresponding N-acetylated derivative was present in the materials analyzed. The inhibitory effect of 2-deoxy-2,3-didehydro-N-glycoloylneuraminic acid on Vibrio cholerae sialidase using N-acetylneuraminyl-(alpha 2----3)-lactose as substrate is slightly higher (50% inhibition at 10 microM) when compared with 2-deoxy-2,3-didehydro-N-acetylneuraminic acid (50% inhibition at 15 microM).

Animals↗
PubMed1985

Determination of 3-deoxy-D-manno-octulosonic acid (KDO), N-acetylneuraminic acid, and their derivatives by ion-exchange liquid chromatography.

A liquid chromatography (1.6 MPa) system for the analysis of 3-deoxy-D-manno-2-octulosonic acid (KDO), N-acetylneuraminic acid (Neu5Ac), methyl alpha- and beta-glycosides of Neu5Ac and KDO, alpha-heptosyl-(1----5)-KDO, various sialyllactoses, alpha-KDO-(2----4)-KDO, alpha-KDO-(2----4)-KDO methyl alpha-glycoside, beta-KDO-(2----4)-KDO methyl beta-glycoside, D-glucuronic acid, D-glucurono-3,6-lactone, and D-galacturonic acid has been developed. Separation was achieved within 10 and 30 min by the use of a small column filled with a strongly basic, anion-exchange resin, Aminex A-29, and 0.75 or 10mM sodium sulfate solutions as mobile phases. This method allowed the determination of KDO and sialic acids in amounts of 100 ng (0.5 nmol) and 200 pg (0.6 pmol), respectively.

Chromatography, High Pressure Liquid↗
PubMed1985

Sialidase activity in the sera of patients and rabbits with clostridial myonecrosis.

The origin and nature of gas gangrene can be diagnosed exactly only by time-consuming bacteriological tests. In order to improve the diagnostic procedures, rabbits were infected with strains of Clostridium perfringens, Clostridium septicum or Clostridium sordellii. Sialidase activity was found to increase rapidly in serum; elevated creatine kinase activities were observed, too. High sialidase concentrations were found in sera (up to 1.6 mU/ml) and in tissues of wounded regions (up to 110 mU/g) of patients diagnosed to be infected with C. perfringens. By inhibition of enzyme activity with antibodies specific for the sialidase from this Clostridium species, it was possible to identify the clostridial origin of the sialidase activities. In the same material from other patients supposed to suffer from gas gangrene, but where no Clostridia could be detected, significant sialidase activity was not found. Thus, sialidase may be a useful tool for the diagnosis of myonecrosis due to clostridial infection.

Adolescent↗
PubMed1985

Structural analysis of underivatized sialic acids by combined high-performance liquid chromatography-mass spectrometry.

Mass spectra of chemically ionized, positive ions of underivatized N,O-acylated sialic acids, 2-deoxy-2,3-didehydro-N-acetylneuraminic acid and sialyl-alpha(2-3)-lactose were obtained by combined high-performance liquid chromatography--mass spectrometry, using a direct liquid inlet system. The mass spectra of the different compounds for which fragmentation schemes are proposed enable the differentiation between sialic acids, although the localization of O-substituents is not possible. However, since the various sialic acids separated well on high-performance liquid chromatography, combined high-performance liquid chromatography-mass spectrometry allowed their unequivocal characterization.

Animals↗
PubMed1985

The receptor-destroying enzyme of influenza C virus is neuraminate-O-acetylesterase.

The nature of the receptor-destroying enzyme (RDE) of influenza C virus has been elucidated by analyzing its effect on the haemagglutination inhibitors rat alpha 1-macroglobulin (RMG) and bovine submandibulary mucin (BSM), respectively. The inhibitory activity of both compounds is abolished by incubation with influenza C virus. After inactivation, RMG and BSM were found to contain reduced amounts of N-acetyl-9-O-acetylneuraminic acid (Neu5,9Ac2) and increased amounts of N-acetylneuraminic acid (Neu5Ac). H.p.l.c. analysis revealed that purified Neu5,9Ac2 is converted to Neu5Ac by incubation with influenza C virus. These results demonstrate that RDE of influenza C virus is neuraminate-O-acetylesterase [N-acyl-9(4)-O-acetylneuraminate O-acetylhydrolase (EC 3.1.1.53)]. The data also indicate that haemagglutination-inhibition (HI) by RMG and BSM and most likely virus attachment to cell surfaces involves binding of influenza C virus to Neu5,9Ac2.

Acetylesterase↗
PubMed1985

Fluorescent staining of sialidases in polyacrylamide gel electrophoresis and ultrathin-layer isoelectric focusing.

Polyacrylamide gels were stained with the sialidase substrate 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid showing the activity of Vibrio cholerae and Clostridium sordellii sialidases in the gels after electrophoresis. With this fluorogenic method minimum sialidase activities of 5 microU could be determined. The sensitivity of this staining is about 10,000-fold higher compared to protein-staining with Coomassie brilliant blue. For the visualization of other proteins than sialidases the specific sialidase staining could be followed by a protein-staining method in the same gel.

Chemical Phenomena↗
PubMed1985

Analysis of gangliosides using fast atom bombardment mass spectrometry.

The native gangliosides GM3, GM1, Fuc-GM1, GD1a, GD1b, Fuc-GD1b, GT1b and GQ1b were analysed by fast atom bombardment mass spectrometry (FAB-MS) in the negative ion mode in a matrix of thioglycerol. After permethylation the same gangliosides were analysed by electron impact (EI) and FAB-MS in the positive ion mode. The negative ion mass spectra furnished information on the molecular weight, the ceramide moiety and the sequence of carbohydrate residues. The sites of attachment and the number of sialic acids present could be deduced directly from the pattern of sequence ions. After addition of sodium acetate positive ion FAB-spectra of the permethylated samples show intense pseudomolecular ions M + Na, that provide evidence on the homogeneity of the samples. In addition, the ceramide part, the oligosaccharide moiety obtained after cleavage of the glycosidic bond of the hexosamine residue, the whole carbohydrate chain and the sialic acids are represented by specific fragment ions. With EI-MS further information can be obtained on the sphingosine and fatty acid components of the ceramide residue. The data show, that the combination of soft ionization mass spectrometry with classical EI-MS gives valuable information on the structure and homogeneity of gangliosides. The method is also applicable to the structural elucidation or quantitation of more complex gangliosides or glycolipid mixtures using only micrograms of material.

Animals↗
PubMed1985

Correlative properties for a differentiation of two Clostridium sordellii phenotypes and their distinction from Clostridium bifermentans.

As the present classification (19) of Clostridium sordellii and C. bifermentans is based on properties which are not conclusive for most of our strains, we investigated 80 strains from various origin of this group regarding 30 selected properties. Four of these properties were correlative and therefore particularly important for a distinct differentiation of the strains investigated: urease activity (U), growth inhibition by 1% mannose (M), arginine deaminase activity (A), and sialidase (EC 3.2.1.18) activity (S). Concerning these four characters three clusters were formed: cluster I was positive for U, M, A, and S and comprised 36 strains including C. sordellii type strain (ATCC 9714T); cluster II was positive for M and S and negative for U and A and comprised twelve strains including strain ATCC 35392; and cluster III was positive for A and negative for U, M, and S and comprised 32 strains including C. bifermentans type strain (ATCC 638T). Only two of the correlative properties (U and S, U and A, A and M, or A and S) needed to be tested to determine the affiliation of any strain of the C. sordellii/bifermentans group to one of the three clusters. Clusters I and II, representing two phenotypes of C. sordellii, can now clearly be distinguished from C. bifermentans. Sialidase formed by cluster I and II strains was inhibited by antibodies produced against cluster I strain sialidase. No cross reaction was found with other clostridial sialidases. Pathogenicity, hitherto considered as one of the distinctive properties of C. sordellii and C. bifermentans, was found with various strains of all the three clusters. Therefore, in the case of an infection caused by these two species, care should be taken as to the pathogenicity especially of C. bifermentans and treatment should be accordingly.

Animals↗
PubMed1985

Studies on the interaction of Clostridium perfringens sialidase with sialic acid linked to the internal galactose in monosialogangliotetraosyl ceramide.

Investigation of the action of highly purified Clostridium perfringens sialidase on ganglioside II3Neu5Ac-Gg4Cer and its oligosaccharide II3Neu5Ac-Gg4, in the presence and absence of sodium cholate, extend earlier results obtained with impure enzyme fractions. Sialidase labeled with 125I was found to bind to various ganglioside substrate micelles, including II3Neu5Ac-Gg4Cer, and to mixed ganglioside-sodium cholate micelles. No binding occurred between the enzyme and the ganglioside-derived oligosaccharide II3Neu5Ac-Gg4, even when radioactive II3Neu5Ac-Gg4-[3H]ol was used. The binding of sialidase to micellar substrate is a condition for enzymic hydrolysis. Correspondingly, II3Neu5Ac-Gg4Cer and II3Neu5Ac-Gg4Cer-sodium cholate micelles were hydrolyzed by the enzyme but II3Neu5Ac-Gg4 was not. Ganglioside oligosaccharide analogues containing an amino function at the reducing terminus or between two oligosaccharide chains, II3Neu5Ac-Gg4-NH2 and (II3Neu5Ac-Gg4)2NH, were hydrolyzed in the absence of cholate. A synthetic analogue of II3Neu5Ac-Gg4Cer containing only the fatty acid moiety and not the sphingosine residue (I1-deoxy-I1-stearamido-II3-monosialo-gangliotetraitol ) behaved as the ganglioside in the presence and absence of sodium cholate.

Chemical Phenomena↗
PubMed1985

Isolation and characterization of gangliosides from pig lymphocytes.

Two major gangliosides from pig spleen lymphocytes, accounting for 57% of the total lipid-bound sialic acids, were isolated and purified to homogeneity by column chromatography on DEAE-Sephadex and silica gel. They were identified as GM3 (II3Neu5GcLacCer), and GD3 (II3(Neu5Gc)2LacCer), by thin-layer chromatography in comparison with standards and by analysis of the constituent sugars. The major fatty acids of these gangliosides were stearic acid and myristic acid, respectively. In addition to these gangliosides, GD2 and bands comigrating on thin-layer chromatography with authentic GM2, GM1, GD1a and GD1b were found. These compounds also occur in pig peripheral blood lymphocytes, where, however, GD3 represents about 70% of the total lipid-bound sialic acid.

Animals↗
PubMed1984

Chemical behaviour of cytidine 5'-monophospho-N-acetyl-beta-D-neuraminic acid under neutral and alkaline conditions.

The chemical behaviour of CMP-N-acetylneuraminic acid under neutral and different alkaline conditions has been investigated. The products formed were isolated by ion-exchange chromatography and gel filtration and analysed by colorimetric methods, thin-layer chromatography, combined gas-liquid chromatography/mass spectrometry and/or 360-MHz 1H-NMR spectroscopy. A maximum stability of CMP-N-acetylneuraminic acid was observed at pH8-11. In the tested pH range of 6-13, CMP and N-acetylneuraminic acid were formed in variable amounts as decomposition products. 2-Deoxy-2,3-dehydro-N-acetylneuraminic acid was produced at pH greater than 7; the amount of this substance increased with increasing pH. In anhydrous triethylamine its yield was 50%. A new neuraminic acid derivative, N-acetyl-beta-D-neuraminic acid 2-phosphate, could be isolated from the mixture of alkaline decomposition products of CMP-N-acetylneuraminic acid. The yield of this compound was maximum 22% in anhydrous triethylamine. Because 2-deoxy-2,3-dehydro-N-acetylneuraminic acid was formed under simulated physiological conditions, it is assumed that this compound, which occurs in tissues and fluids of man and animals, is derived from CMP-N-acetylneuraminic acid non-enzymically also under conditions in vivo.

Chemical Phenomena↗
PubMed1984

New techniques for the investigation of structure and metabolism of sialic acids.

Sialic acid analysis in biological material including gangliosides is often confronted with the necessity to determine trace amounts of various N,O-substituted species. Therefore, techniques of high sensitivity and resolution are required, such as capillary gas-liquid chromatography (GLC) and high performance liquid chromatography (HPLC). Both methods in combination with mass spectrometry allow structural analysis of the different neuraminic acid derivatives. Thus, the number of natural sialic acids known so far has increased to more than 30, including non only saturated, but also 2,3-unsaturated and 2,7-anhydro-sialic acids. Furthermore, HPLC has proved to be especially useful for the study of enzyme reactions, as the sialic acids of enzyme assay mixtures in most cases can be analyzed without prior extensive purification or derivatization.

Animals↗
PubMed1984

Malaria parasites do not contain or synthesize sialic acids.

The capacity of Plasmodia to synthesize sialic acids was investigated by adding radioactive acetate to short-term in vitro cultures of the intraerythrocytic asexual forms of three malaria parasites (the human malaria Plasmodium falciparum in Aotus trivirgatus erythrocytes; the simian malaria P. knowlesi in rhesus monkey erythrocytes; the rodent malaria P. berghei in mouse erythrocytes) and to cultures of extracellular zygotes of the avian malaria P. gallinaceum. Radioactive acetate was added to normal rhesus monkey erythrocytes and to cells of the murine myeloma NS-1 for comparison. Although [1-14C]-acetate labeled many proteins with each malaria parasite and the NS-1 cells, analysis of purified sialic acids revealed that only with the NS-1 cells was radioactivity incorporated into sialic acids. Furthermore, N-acetyl[6-3H]mannosamine was not incorporated into sialic acids or malarial glycoproteins when added to P. knowlesi cultures. All of the malaria parasites underwent growth or differentiation during these experiments as measured by [35S]methionine uptake into protein and by light microscopy. Extracellular parasites largely free of erythrocyte membranes were prepared to determine whether Plasmodia contain sialic acids that are not labeled by exogenous precursors. Purified merozoites of P. knowlesi and zygotes of P. gallinaceum did not contain detectable amounts of sialic acids on chemical analysis. Thus, although we could show that Plasmodia can incorporate radioactive sugars such as glucosamine, galactose and mannose into proteins, presumably glycoproteins, they do not synthesize sialic acids or sialo-glycoproteins, nor do they contain sialo-glycoconjugates of host origin.

Animals↗
PubMed1984

Isolation and characterization of an oligosaccharide- and glycoprotein-specific sialidase from human leucocytes.

A sialidase was solubilized with the aid of Triton X-100 from the insoluble material of a leucocyte homogenate. The enzyme was purified almost to homogeneity by chromatography on Sephadex G-75, equine submandibular gland mucin bound to Sepharose 4B and on Sephacryl S-200. The purification factor was 40 based on an increase of the specific enzyme activity from the Triton X-100 extract (pure enzyme: 40 mU/mg protein). Isolation of the active enzyme required the presence of a proteinase inhibitor. The sialidase is monomeric and has an average molecular mass of 48500 Da, a pH optimum of 4.6, hydrolyses preferably glycoprotein (fetuin) and sialyllactose, is activated by Ca2 and inhibited by N-acetyl-2,3-dehydro-2- deoxyneuraminic acid ( Neu5Ac2en ), Hg2 and N-(4-nitrophenyl) oxamic acid. The relatively stable enzyme shows only low activity with gangliosides and no activity with 4-O-acetylated sialic acid bound glycosidically.

Blood Proteins↗