PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “NEURAMINIDASE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 793 records · Page 44Linked to original sources
PubMed1999

Aggregated human serum immunoglobulin A1 induced by neuraminidase treatment had a lower number of O-linked sugar chains on the hinge portion.

A part of human serum immunoglobulin A1(IgA1) was aggregated by treatment with neuraminidase. Aggregated IgA1 was separated from non-aggregated IgA1 by gel permeation chromatography. The prepared asialo-hinge glycopeptide (asialo-HGP) from both IgA1 subfractions was treated with beta-galactosidase to determine the number of beta-linked sugar chains attached on the hinge region. Removal of the galactose residue from asialo-HGP resulted in the HPLC separation of three major peaks. MALDI-TOFMS analysis of the glycopeptides also indicated the presence of three HGP components with three, four and five N-acetylgalactosamine (GalNAc) residues, respectively. Comparison of their relative content among the glycopeptide components showed a higher content of the HGP component with a lower number of GalNAc residues on aggregated IgA1. Thus, asialo-HGP prepared from aggregated IgA1 induced by neuraminidase treatment had an incomplete core structure of O-linked oligosaccharides. Especially, the result suggested that the reduced number of the attached O-linked oligosaccharides on IgA1 take part in phenomena such as self-aggregation of asialo-IgA1.

Amino Acid Sequence↗
PubMed1989

Characterization of extracellular neuraminidase produced by Actinomyces pyogenes.

Extracellular neuraminidase from Actinomyces pyogenes could be isolated by ammonium sulfate precipitation, ion exchange chromatography with DEAE cellulose and gel filtration on Ultrogel ACA 54. The purified enzyme had a molecular weight of approximately 50,000 Dalton, a pH optimum at pH 6.0, a temperature optimum at 55 degrees C and a Km value of 1.4 X 10(-4) mol/l with N-acetyl-neuraminlactose as substrate. Preparative isoelectric focussing of the culture supernatant revealed neuraminidase activity mainly at pH 6.5. The enzyme activity was not influenced by metalions or EDTA.

Actinomyces↗
PubMed2000

Inhibition of neuraminidase with neuraminic acid C-glycosides.

Neuraminic (sialic) acid based alpha-C-glycosides have been synthesized and their inhibitory activity towards bacterial neuraminidase (sialidase) was examined. While some C-glycosides were found to be potent inhibitors (Ki 15-30 microM) of this neuraminidase, others afforded no measurable activity. The structure-activity relationship of these C-glycosides is discussed in the context of other previously reported sialidase inhibitors.

Buffers↗
PubMed1976

A surface antigen influenza vaccine. 1. Purification of haemagglutinin and neuraminidase proteins.

Influenza virus was centrifuged in a KII rotor through a sucrose gradient containing Triton N101, a non-ionic surfactant. The micelles of surfactant formed a band in the gradient. As virus particles passed through the surfactant, the haemagglutinin and neuraminidase proteins were stripped from the surface and remained near the surfactant micelles. The residual virus particles sedimented into a denser region of the gradient and were thus separated from the haemagglutinin and neuraminidase antigens. Fractions containing the surface antigens were pooled and Triton was removed by phase-separation at the cloud point.

Agglutinins↗
PubMed1984

An investigation of antigenic drift of neuraminidases of influenza A (H1N1) viruses.

A newly developed lectin neuraminidase test (LNT) and a panel of mouse monoclonal and post-infection ferret antibodies have been used to analyse antigenic drift in N1 neuraminidases of influenza A viruses isolated between 1933 and 1957 and also between 1977 and 1980. Significant antigenic differences were detected among the 'early' (1933-57) viruses since the NA of viruses isolated one year apart could be distinguished serologically. The NA of the 're-emerged' virus A/USSR/92/77 (H1N1) was antigenically related but not identical to influenza A viruses isolated in 1949 (A/Paris/49 (H1N1), A/Geneva/49 (H1N1) which thus predates the previously observed antigenic similarity of A/USSR/77 with A/FW/50 (H1N1) virus.

Animals↗
PubMed1984

Modulation of neuraminidase activity by the physical state of phospholipid bilayers containing gangliosides Gd1a and Gt1b.

The thermotropic behavior of large unilamellar dipalmitoylphosphatidylcholine vesicles containing the disialoganglioside Gd1a and the trisialoganglioside Gt1b on their outer surface has been studied as a function of the ganglioside molar fraction and Ca2+ concentration by using high-sensitivity differential scanning calorimetry and steady-state fluorescence spectroscopy. These studies indicate that both gangliosides have an ordering effect on the hydrocarbon region of the bilayer and that this effect is enhanced by the presence of Ca2+ ions. The calorimetric experiments also indicate that ganglioside Gt1b has an intrinsic tendency to phase separate into compositional-rich ganglioside domains even in the absence of Ca2+. Ganglioside Gd1a, on the other hand, only phase separates at Ca2+ concentrations equal to or higher than 10 mM. These studies have allowed us to identify and evaluate the factors affecting the rates of hydrolysis of gangliosides by the soluble neuraminidase from Clostridium perfringens. The data presented in this paper indicate that the rates of hydrolysis of membrane-bound gangliosides are correlated to the physical state of the membrane and the state of aggregation of the ganglioside molecules within the lipid bilayer. For membrane-bound gangliosides, maximal activation energies were found at temperatures slightly below the lipid phase transition temperature. The rates of hydrolysis of the soluble substrate sialyllactose or that of the micellar ganglioside is independent of Ca2+ concentration, whereas the rates of hydrolysis of membrane-bound ganglioside are inhibited by Ca2+ especially under conditions in which the clustering effect of Ca2+ is maximal. These studies suggest that the soluble neuraminidases from Clostridium perfringens prefer ganglioside substrates that are dispersed within the membrane and not forming part of largely aggregated clusters.

Calcium↗
PubMed1985

Use of virus-attached antibodies or insulin molecules to mediate fusion between Sendai virus envelopes and neuraminidase-treated cells.

Anti-human erythrocyte antibodies or insulin molecules were covalently coupled to the glycoproteins (the hemagglutinin/neuraminidase and the fusion polypeptides) of Sendai virus envelopes with N-succinimidyl 3-(2-pyridyldithio)propionate and succinimidyl 4-(p-maleimidophenyl)butyrate as cross-linking reagents. Reconstituted Sendai virus envelopes, bearing covalently attached anti-human erythrocyte antibodies or insulin molecules, were able to bind to but not fuse with virus receptor depleted human erythrocytes (neuraminidase-treated human erythrocytes). Only coreconstitution of Sendai virus glycoproteins, bearing attached anti-human erythrocyte antibodies or insulin molecules with intact, untreated viral glycoproteins, led to the formation of fusogenic, targeted reconstituted Sendai virus envelopes. Binding and fusion of reconstituted Sendai virus envelopes, bearing anti-human erythrocyte antibodies or insulin molecules, with neuraminidase-treated human erythrocytes were blocked by the monovalent fraction, obtained after papain digestion of immunoglobulins, made of anti-human erythrocyte antibodies or free insulin molecules, respectively. The results of this work demonstrate an active role of the viral binding protein (hemagglutinin/neuraminidase polypeptide) in the virus membrane fusion process and show a novel and efficient method for the construction of targeted, fusogenic Sendai virus envelopes.

Antibodies↗
PubMed1986

Radiation inactivation analysis of influenza virus reveals different target sizes for fusion, leakage, and neuraminidase activities.

The size of the functional units responsible for several activities carried out by the influenza virus envelope glycoproteins was determined by radiation inactivation analysis. Neuraminidase activity, which resides in the glycoprotein NA, was inactivated exponentially with an increasing radiation dose, yielding a target size of 94 +/- 5 kilodaltons (kDa), in reasonable agreement with that of the disulfide-bonded dimer (120 kDa). All the other activities studied are properties of the HA glycoprotein and were normalized to the known molecular weight of the neuraminidase dimer. Virus-induced fusion activity was measured by two phospholipid dilution assays: relief of energy transfer between N-(7-nitro-2,1,3-benzoxadiazol-4-yl)dipalmitoyl-L-alpha- phosphatidylethanolamine (N-NBD-PE) and N-(lissamine rhodamine B sulfonyl)-dioleoyl-L-alpha-phosphatidylethanolamine (N-Rh-PE) in target liposomes and relief of self-quenching of N-Rh-PE in target liposomes. Radiation inactivation of fusion activity proceeded exponentially with radiation dose, yielding normalized target sizes of 68 +/- 6 kDa by assay i and 70 +/- 4 kDa by assay ii. These values are close to the molecular weight of a single disulfide-bonded (HA1 + HA2) unit (75 kDa), the "monomer" of the HA trimer. A single monomer is thus inactivated by each radiation event, and each monomer (or some part of it) constitutes a minimal functional unit capable of mediating fusion. Virus-induced leakage of calcein from target liposomes and virus-induced leakage of hemoglobin from erythrocytes (hemolysis) both showed more complex inactivation behavior: a pronounced shoulder was present in both inactivation curves, followed by a steep drop in activity at higher radiation levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Synthesis of 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid and detection of skin fibroblast neuraminidase in normal humans and in sialidosis.

A procedure for the synthesis of the fluorogenic substrate analogue 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid for the human acid neuraminidase has been developed. The substrate was employed for the characterization of the enzyme in sonicates of cultured human skin fibroblasts and for enzymatic detection of the neuraminidase deficiency in the neurological storage disorder, sialidosis. Synthesis was accomplished by reacting 2-deoxy-2-chloro-4,7,8,9-tetra-O-acetyl-N-acetylneuraminic acid methyl ester with the sodium salt of 4-methylumbelliferone in acetonitrile at room temperature. The coupled product was purified on silicic acid chromatography, followed by base-catalyzed removal of the O-acetyl and methoxy blocking groups, and with additional purification of the hydrolyzed product on silicic acid. The overall yield, based on N-acetylneuraminic acid, was 37%. Under linear assay conditions, at pH 4.3, the apparent maximal velocities (nmol (mg of protein)-1 h-1) for normal fibroblasts were 58--115, 0.2--1.8 for sialidosis fibroblasts, and 28--38 for obligate heterozygotes. The apparent Km for normals was 0.13 mM.

Adult↗
PubMed1998

Critical interactions in binding antibody NC41 to influenza N9 neuraminidase: amino acid contacts on the antibody heavy chain.

Antibody NC41 binds to the subtype N9 neuraminidase (NA) of influenza virus A/tern/Australia/ G70c/75 and inhibits its enzyme activity. To address the molecular mechanisms by which antibodies interact with neuraminidase and the requirements for successful escape from antibody inhibition, we made amino acid substitutions in heavy chain CDRs of NC41. Antibody proteins expressed as a single-chain Fv (scFv) fused with maltose-binding protein were assayed for binding to NA by ELISA. Association constants (Ka) for wild-type and mutant scFvs are as follows: wild type, 2 x 10(7) M-1; Asn31-->Gln, 2 x 10(7) M-1; Glu96-->Asp, 1 x 10(7) M-1; Asp97-->Lys, 6 x 10(6) M-1; and Asn98-->Gln, 8 x 10(6) M-1. The Ka for intact NC41 antibody was 4 x 10(8) M-1 in the same assay, reflecting increased stability compared to that of the scFv. Mutations in the scFv antibody had less of an effect on binding than mutations in their partners on the NA, and modeling studies suggest that interactions involving the mutant antibody side chains occur, even without taking increased flexibility into account. Asp97 forms a salt link with NA critical contact Lys434; of the four mutants, D97K shows the largest reduction in binding to NA. Mutant N98Q also shows reduced binding, most likely through the loss of interaction with NA residue Thr401. Substitution N31Q had no effect on Ka. NC41 residue Glu96 interacts with NA critical contact Ser368, yet E96D showed only a 2-fold reduction in binding to NA, apparently because the H bond can still form. Asp97 and Asn98 provide the most important interactions, but some binding is maintained when they are mutated, in contrast to their partners on the NA. The results are consistent with maturation of the immune response, when the protein epitope is fixed while variation in the antibody paratope allows increasing affinity. Influenza viruses may exploit this general mechanism since single amino acid changes in the epitope allow the virus to escape from the antibody.

Amino Acid Sequence↗
PubMedDate not supplied

Influenza virus neuraminidase inhibitors: generation and comparison of structure-based and common feature pharmacophore hypotheses and their application in virtual screening.

X-ray crystallographic data of the influenza virus neuraminidase in complex with different inhibitors were used to generate chemical feature-based pharmacophore models of the binding site of this enzyme. The models were built using the software package Catalyst. Pharmacophore hypotheses derived from the 3-D structure of ligands cocrystallized with the enzyme were then compared with automatically generated common feature pharmacophore hypotheses for neuraminidase inhibitors. The latter models were found to contain fewer features and exhibited lower selectivity in virtual screening experiments. Some functions of the inhibitors obviously participate in more than one mode of interaction with the enzyme (charge-charge interaction and hydrogen bond) or form hydrogen bonds to several amino acids. Since such multiple interactions of one chemical function cannot be included into the Catalyst data format, strategies are presented to overcome these limitations. Finally, the results of 3-D database searching experiments using these hypotheses are described.

Crystallography, X-Ray↗
PubMed2006

Optimal charges in lead progression: a structure-based neuraminidase case study.

Collective experience in structure-based lead progression has found electrostatic interactions to be more difficult to optimize than shape-based ones. A major reason for this is that the net electrostatic contribution observed includes a significant nonintuitive desolvation component in addition to the more intuitive intermolecular interaction component. To investigate whether knowledge of the ligand optimal charge distribution can facilitate more intuitive design of electrostatic interactions, we took a series of small-molecule influenza neuraminidase inhibitors with known protein cocrystal structures and calculated the difference between the optimal and actual charge distributions. This difference from the electrostatic optimum correlates with the calculated electrostatic contribution to binding (r(2) = 0.94) despite small changes in binding modes caused by chemical substitutions, suggesting that the optimal charge distribution is a useful design goal. Furthermore, detailed suggestions for chemical modification generated by this approach are in many cases consistent with observed improvements in binding affinity, and the method appears to be useful despite discrete chemical constraints. Taken together, these results suggest that charge optimization is useful in facilitating generation of compound ideas in lead optimization. Our results also provide insight into design of neuraminidase inhibitors.

Binding Sites↗
PubMed2000

Synthesis of 6-acetamido-5-amino- and -5-guanidino-3, 4-dehydro-N-(2-ethylbutyryl)- 3-piperidinecarboxylic acids related to zanamivir and oseltamivir, inhibitors of influenza virus neuraminidases.

[reaction: see text] 6-Acetamido-5-amino- and -5-guanidino-3, 4-dehydro-N-(2-ethylbutyryl)-3-piperidinecarboxylic acids (8 and 9) have been synthesized starting from natural siastatin B, a bacterial neuraminidase inhibitor isolated from Streptomyces culture in a stereospecific fashion. These compounds are related to zanamivir and oseltamivir, inhibitors of influenza virus neuraminidases.

Acetamides↗
PubMed1999

The sensitivity of the results of molecular docking to induced fit effects: application to thrombin, thermolysin and neuraminidase.

This paper describes the application of PRO_LEADS to the flexible docking of ligands into crystallographically derived enzyme structures that are assumed to be rigid. PRO_LEADS uses a Tabu search methodology to perform the flexible search and an empirically derived estimate of the binding affinity to drive the docking process. The paper tests the extent to which the assumption of a rigid enzyme compromises the accuracy of the results. All-pairs docking experiments are performed for three enzymes (thrombin, thermolysin and influenza virus neuraminidase) based on six or more ligand-enzyme crystal structures for each enzyme. In 76% of the cases, PRO_LEADS can successfully identify the correct ligand conformation as the lowest energy configuration when the enzyme structure is derived from that ligand's crystal structure, but the methodology only docks 49% of the cases successfully when the ligand is docked against enzyme crystal structures derived from other ligands. Small movements in the enzyme structure lead to an under-prediction in the energy of the correct binding mode by up to 14 kJ/mol and in some cases this under-prediction can lead to the native mode not being recognised as the lowest energy solution. The type of movements responsible for mis-docking are: the movement of sidechains as a result of changes in C alpha position; the movement of sidechains without changes in C alpha position; the movement of flexible portions of main chains to facilitate the formation of hydrogen bonds; and the movement of metal atoms bound to the enzyme active site. The work illustrates that the assumption of a rigid active site can lead to errors in identification of the correct binding mode and the assessment of binding affinity, even for enzymes which show relatively small shift in atomic positions from one ligand to the next. A good docking code, such as PRO_LEADS, can usually dock successfully if there is induced fit in relatively rigid enzymes but there remains the need to develop improved strategies for dealing with enzyme flexibility. The work implies that treatments of enzyme flexibility which focus only on sidechain rotations will not deal with the critical shifts responsible for mis-docking of ligands in thrombin, thermolysin and neuraminidase. The paper demonstrates the utility of all pairs docking experiments as a method of assessing the effectiveness of docking methodologies in dealing with enzyme flexibility.

Binding Sites↗
PubMed2003

Phylogenetic analysis of neuraminidase gene of H9N2 influenza viruses prevalent in chickens in China during 1995-2002.

The neuraminidase (NA) genes of 12 H9N2 influenza virus strains isolated from diseased chickens in different farms in mainland China during 1995-2002 were amplified and sequenced. Amino acids at hemadsorbing (HB) site of these isolates are different from those of A/quail/Hong Kong/G1/97-like viruses and A/chicken/Korea/96-like viruses. Neuraminidases of the 12 strains had a deletion of 3 amino acid residues at positions 63-65 as compared to that of A/turkey/Wisconsin/189/66, while those of Korea and Pakistan H9N2 isolates had no deletion. Phylogenetic analyses showed NA gene of these isolates belonged to that of A/duck/Hong Kong/Y280/97-like virus lineage. NA gene of the H9N2 viruses isolated in Korea and Pakistan belonged to lineage different from those of the 12 isolates. The present results indicate that the NA of H9N2 strains isolated in mainland China during the past 8 years were well preserved and the geographical distribution play a significant role in the evolution of the H9N2 influenza viruses.

Animals↗