Neuraminidase: An enzyme that catalyzes the hydrolysis of alpha-2,3, alpha-2,6-, and alpha-2,8-glycosidic linkages (at a decreasing rate, respectively) of terminal sialic residues in oligosaccharides, glycoproteins, glycolipids, colominic acid, and synthetic substrate. (From Enzyme Nomenclature, 1992)Zanamivir: A guanido-neuraminic acid that is used to inhibit NEURAMINIDASE.Sialic Acids: A group of naturally occurring N-and O-acyl derivatives of the deoxyamino sugar neuraminic acid. They are ubiquitously distributed in many tissues.Oseltamivir: An acetamido cyclohexene that is a structural homolog of SIALIC ACID and inhibits NEURAMINIDASE.Influenza A virus: The type species of the genus INFLUENZAVIRUS A that causes influenza and other diseases in humans and animals. Antigenic variation occurs frequently between strains, allowing classification into subtypes and variants. Transmission is usually by aerosol (human and most non-aquatic hosts) or waterborne (ducks). Infected birds shed the virus in their saliva, nasal secretions, and feces.PyransNeuraminic AcidsOrthomyxoviridae: A family of RNA viruses causing INFLUENZA and other diseases. There are five recognized genera: INFLUENZAVIRUS A; INFLUENZAVIRUS B; INFLUENZAVIRUS C; ISAVIRUS; and THOGOTOVIRUS.N-Acetylneuraminic Acid: An N-acyl derivative of neuraminic acid. N-acetylneuraminic acid occurs in many polysaccharides, glycoproteins, and glycolipids in animals and bacteria. (From Dorland, 28th ed, p1518)Hemagglutinin Glycoproteins, Influenza Virus: Membrane glycoproteins from influenza viruses which are involved in hemagglutination, virus attachment, and envelope fusion. Fourteen distinct subtypes of HA glycoproteins and nine of NA glycoproteins have been identified from INFLUENZA A VIRUS; no subtypes have been identified for Influenza B or Influenza C viruses.Influenza, Human: An acute viral infection in humans involving the respiratory tract. It is marked by inflammation of the NASAL MUCOSA; the PHARYNX; and conjunctiva, and by headache and severe, often generalized, myalgia.Hemagglutination, Viral: Agglutination of ERYTHROCYTES by a virus.Guanidines: A family of iminourea derivatives. The parent compound has been isolated from mushrooms, corn germ, rice hulls, mussels, earthworms, and turnip juice. Derivatives may have antiviral and antifungal properties.Antiviral Agents: Agents used in the prophylaxis or therapy of VIRUS DISEASES. Some of the ways they may act include preventing viral replication by inhibiting viral DNA polymerase; binding to specific cell-surface receptors and inhibiting viral penetration or uncoating; inhibiting viral protein synthesis; or blocking late stages of virus assembly.Influenza A Virus, H1N1 Subtype: A subtype of INFLUENZA A VIRUS with the surface proteins hemagglutinin 1 and neuraminidase 1. The H1N1 subtype was responsible for the Spanish flu pandemic of 1918.Hemagglutinins, Viral: Specific hemagglutinin subtypes encoded by VIRUSES.Orthomyxoviridae Infections: Virus diseases caused by the ORTHOMYXOVIRIDAE.Influenza B virus: Species of the genus INFLUENZAVIRUS B that cause HUMAN INFLUENZA and other diseases primarily in humans. Antigenic variation is less extensive than in type A viruses (INFLUENZA A VIRUS) and consequently there is no basis for distinct subtypes or variants. Epidemics are less likely than with INFLUENZA A VIRUS and there have been no pandemics. Previously only found in humans, Influenza B virus has been isolated from seals which may constitute the animal reservoir from which humans are exposed.Influenza A Virus, H3N2 Subtype: A subtype of INFLUENZA A VIRUS comprised of the surface proteins hemagglutinin 3 and neuraminidase 2. The H3N2 subtype was responsible for the Hong Kong flu pandemic of 1968.Influenza A Virus, H5N1 Subtype: A subtype of INFLUENZA A VIRUS comprised of the surface proteins hemagglutinin 5 and neuraminidase 1. The H5N1 subtype, frequently referred to as the bird flu virus, is endemic in wild birds and very contagious among both domestic (POULTRY) and wild birds. It does not usually infect humans, but some cases have been reported.Influenza in Birds: Infection of domestic and wild fowl and other BIRDS with INFLUENZA A VIRUS. Avian influenza usually does not sicken birds, but can be highly pathogenic and fatal in domestic POULTRY.Drug Resistance, Viral: The ability of viruses to resist or to become tolerant to chemotherapeutic agents or antiviral agents. This resistance is acquired through gene mutation.Galactose Oxidase: An enzyme that oxidizes galactose in the presence of molecular oxygen to D-galacto-hexodialdose. It is a copper protein. EC 1.1.3.9.Ferrets: Semidomesticated variety of European polecat much used for hunting RODENTS and/or RABBITS and as a laboratory animal. It is in the subfamily Mustelinae, family MUSTELIDAE.Hemagglutination Inhibition Tests: Serologic tests in which a known quantity of antigen is added to the serum prior to the addition of a red cell suspension. Reaction result is expressed as the smallest amount of antigen which causes complete inhibition of hemagglutination.Hemagglutinins: Agents that cause agglutination of red blood cells. They include antibodies, blood group antigens, lectins, autoimmune factors, bacterial, viral, or parasitic blood agglutinins, etc.HN Protein: Glycoprotein from Sendai, para-influenza, Newcastle Disease, and other viruses that participates in binding the virus to cell-surface receptors. The HN protein possesses both hemagglutinin and neuraminidase activity.Reassortant Viruses: Viruses containing two or more pieces of nucleic acid (segmented genome) from different parents. Such viruses are produced in cells coinfected with different strains of a given virus.Lectins: Proteins that share the common characteristic of binding to carbohydrates. Some ANTIBODIES and carbohydrate-metabolizing proteins (ENZYMES) also bind to carbohydrates, however they are not considered lectins. PLANT LECTINS are carbohydrate-binding proteins that have been primarily identified by their hemagglutinating activity (HEMAGGLUTININS). However, a variety of lectins occur in animal species where they serve diverse array of functions through specific carbohydrate recognition.Acetamides: Derivatives of acetamide that are used as solvents, as mild irritants, and in organic synthesis.Influenza A Virus, H2N2 Subtype: A subtype of INFLUENZA A VIRUS comprised of the surface proteins hemagglutinin 2 and neuraminidase 2. The H2N2 subtype was responsible for the Asian flu pandemic of 1957.Influenza A Virus, H7N9 Subtype: A subtype of INFLUENZA A VIRUS with the surface proteins hemagglutinin 7 and neuraminidase 9. This avian origin virus was first identified in humans in 2013.Influenza A Virus, H9N2 Subtype: A subtype of INFLUENZA A VIRUS comprised of the surface proteins hemagglutinin 9 and neuraminidase 2. The H9N2 subtype usually infects domestic birds (POULTRY) but there have been some human infections reported.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Newcastle disease virus: The most well known avian paramyxovirus in the genus AVULAVIRUS and the cause of a highly infectious pneumoencephalitis in fowl. It is also reported to cause CONJUNCTIVITIS in humans. Transmission is by droplet inhalation or ingestion of contaminated water or food.Influenza Vaccines: Vaccines used to prevent infection by viruses in the family ORTHOMYXOVIRIDAE. It includes both killed and attenuated vaccines. The composition of the vaccines is changed each year in response to antigenic shifts and changes in prevalence of influenza virus strains. The vaccine is usually bivalent or trivalent, containing one or two INFLUENZAVIRUS A strains and one INFLUENZAVIRUS B strain.Clostridium perfringens: The most common etiologic agent of GAS GANGRENE. It is differentiable into several distinct types based on the distribution of twelve different toxins.Viral Proteins: Proteins found in any species of virus.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Glycoproteins: Conjugated protein-carbohydrate compounds including mucins, mucoid, and amyloid glycoproteins.Wheat Germ Agglutinins: Lectins purified from the germinating seeds of common wheat (Triticum vulgare); these bind to certain carbohydrate moieties on cell surface glycoproteins and are used to identify certain cell populations and inhibit or promote some immunological or physiological activities. There are at least two isoforms of this lectin.Parainfluenza Virus 3, Human: A species of RESPIROVIRUS frequently isolated from small children with pharyngitis, bronchitis, and pneumonia.Madin Darby Canine Kidney Cells: An epithelial cell line derived from a kidney of a normal adult female dog.Carbohydrates: The largest class of organic compounds, including STARCH; GLYCOGEN; CELLULOSE; POLYSACCHARIDES; and simple MONOSACCHARIDES. Carbohydrates are composed of carbon, hydrogen, and oxygen in a ratio of Cn(H2O)n.Hemadsorption: A phenomenon manifested by an agent or substance adhering to or being adsorbed on the surface of a red blood cell, as tuberculin can be adsorbed on red blood cells under certain conditions. (Stedman, 25th ed)Peanut Agglutinin: Lectin purified from peanuts (ARACHIS HYPOGAEA). It binds to poorly differentiated cells and terminally differentiated cells and is used in cell separation techniques.DucksBirds: Warm-blooded VERTEBRATES possessing FEATHERS and belonging to the class Aves.Cathepsin A: A carboxypeptidase that catalyzes the release of a C-terminal amino acid with a broad specificity. It also plays a role in the LYSOSOMES by protecting BETA-GALACTOSIDASE and NEURAMINIDASE from degradation. It was formerly classified as EC 3.4.12.1 and EC 3.4.21.13.Receptors, Virus: Specific molecular components of the cell capable of recognizing and interacting with a virus, and which, after binding it, are capable of generating some signal that initiates the chain of events leading to the biological response.Gangliosides: A subclass of ACIDIC GLYCOSPHINGOLIPIDS. They contain one or more sialic acid (N-ACETYLNEURAMINIC ACID) residues. Using the Svennerholm system of abbrevations, gangliosides are designated G for ganglioside, plus subscript M, D, or T for mono-, di-, or trisialo, respectively, the subscript letter being followed by a subscript arabic numeral to indicated sequence of migration in thin-layer chromatograms. (From Oxford Dictionary of Biochemistry and Molecular Biology, 1997)Viral Plaque Assay: Method for measuring viral infectivity and multiplication in CULTURED CELLS. Clear lysed areas or plaques develop as the VIRAL PARTICLES are released from the infected cells during incubation. With some VIRUSES, the cells are killed by a cytopathic effect; with others, the infected cells are not killed but can be detected by their hemadsorptive ability. Sometimes the plaque cells contain VIRAL ANTIGENS which can be measured by IMMUNOFLUORESCENCE.Cyclopentanes: A group of alicyclic hydrocarbons with the general formula R-C5H9.Glycosylation: The chemical or biochemical addition of carbohydrate or glycosyl groups to other chemicals, especially peptides or proteins. Glycosyl transferases are used in this biochemical reaction.Hemagglutination Tests: Sensitive tests to measure certain antigens, antibodies, or viruses, using their ability to agglutinate certain erythrocytes. (From Stedman, 26th ed)Paramyxoviridae: A family of spherical viruses, of the order MONONEGAVIRALES, somewhat larger than the orthomyxoviruses, and containing single-stranded RNA. Subfamilies include PARAMYXOVIRINAE and PNEUMOVIRINAE.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Hymecromone: A coumarin derivative possessing properties as a spasmolytic, choleretic and light-protective agent. It is also used in ANALYTICAL CHEMISTRY TECHNIQUES for the determination of NITRIC ACID.Erythrocytes: Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.Periodic Acid: A strong oxidizing agent.Glycoside HydrolasesEnzyme Inhibitors: Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.Mucolipidoses: A group of inherited metabolic diseases characterized by the accumulation of excessive amounts of acid mucopolysaccharides, sphingolipids, and/or glycolipids in visceral and mesenchymal cells. Abnormal amounts of sphingolipids or glycolipids are present in neural tissue. INTELLECTUAL DISABILITY and skeletal changes, most notably dysostosis multiplex, occur frequently. (From Joynt, Clinical Neurology, 1992, Ch56, pp36-7)Molecular Weight: The sum of the weight of all the atoms in a molecule.Hemagglutination: The aggregation of ERYTHROCYTES by AGGLUTININS, including antibodies, lectins, and viral proteins (HEMAGGLUTINATION, VIRAL).Antibodies, Viral: Immunoglobulins produced in response to VIRAL ANTIGENS.Arthrobacter: A genus of asporogenous bacteria isolated from soil that displays a distinctive rod-coccus growth cycle.Pandemics: Epidemics of infectious disease that have spread to many countries, often more than one continent, and usually affecting a large number of people.Amantadine: An antiviral that is used in the prophylactic or symptomatic treatment of influenza A. It is also used as an antiparkinsonian agent, to treat extrapyramidal reactions, and for postherpetic neuralgia. The mechanisms of its effects in movement disorders are not well understood but probably reflect an increase in synthesis and release of dopamine, with perhaps some inhibition of dopamine uptake.Chick Embryo: The developmental entity of a fertilized chicken egg (ZYGOTE). The developmental process begins about 24 h before the egg is laid at the BLASTODISC, a small whitish spot on the surface of the EGG YOLK. After 21 days of incubation, the embryo is fully developed before hatching.Virus Replication: The process of intracellular viral multiplication, consisting of the synthesis of PROTEINS; NUCLEIC ACIDS; and sometimes LIPIDS, and their assembly into a new infectious particle.Sialoglycoproteins: Glycoproteins which contain sialic acid as one of their carbohydrates. They are often found on or in the cell or tissue membranes and participate in a variety of biological activities.Pronase: A proteolytic enzyme obtained from Streptomyces griseus.Electrophoresis, Polyacrylamide Gel: Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.Trypsin: A serine endopeptidase that is formed from TRYPSINOGEN in the pancreas. It is converted into its active form by ENTEROPEPTIDASE in the small intestine. It catalyzes hydrolysis of the carboxyl group of either arginine or lysine. EC 3.4.21.4.Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase: An amidohydrolase that removes intact asparagine-linked oligosaccharide chains from glycoproteins. It requires the presence of more than two amino-acid residues in the substrate for activity. This enzyme was previously listed as EC 3.2.2.18.Actinomycetaceae: A family of bacteria including numerous parasitic and pathogenic forms.Cell Membrane: The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.Chickens: Common name for the species Gallus gallus, the domestic fowl, in the family Phasianidae, order GALLIFORMES. It is descended from the red jungle fowl of SOUTHEAST ASIA.Parainfluenza Virus 1, Human: A species of RESPIROVIRUS also called hemadsorption virus 2 (HA2), which causes laryngotracheitis in humans, especially children.Isoelectric Focusing: Electrophoresis in which a pH gradient is established in a gel medium and proteins migrate until they reach the site (or focus) at which the pH is equal to their isoelectric point.Respirovirus: A genus of the family PARAMYXOVIRIDAE (subfamily PARAMYXOVIRINAE) where all the virions have both HEMAGGLUTININ and NEURAMINIDASE activities and encode a non-structural C protein. SENDAI VIRUS is the type species.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Epitopes: Sites on an antigen that interact with specific antibodies.Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase: A group of related enzymes responsible for the endohydrolysis of the di-N-acetylchitobiosyl unit in high-mannose-content glycopeptides and GLYCOPROTEINS.Oxo-Acid-Lyases: Enzymes that catalyze the cleavage of a carbon-carbon bond of a 3-hydroxy acid. (Dorland, 28th ed) EC 4.1.3.

The effects of digestive enzymes on characteristics of placental insulin receptor. Comparison of particulate and soluble receptor preparations. (1/3160)

The role of the surrounding membrane structure on the binding characteristics of the insulin receptor was studied by using several digestive enzymes. The effects observed with particulate membrane preparations are compared with those from soluble receptor preparations. beta-Galactosidase and neuraminidase had no effect on insulin binding to either particulate or soluble receptors from human placentae. Exposure to 2 units of phospholipase C/ml increased insulin binding to particulate membranes, but was without effect on the soluble receptor preparation. The increase in binding to particulate membranes was shown to be due to an increase in apparent receptor number. After 5 min exposure to 500 microgram of trypsin/ml there was an increase in insulin binding to the particulate membrane fraction, owing to an increase in receptor affinity. After 15 min exposure to this amount of trypsin, binding decreased, owing to a progressive decrease in receptor availability. In contrast, this concentration of trypsin had no effect on the solubilized receptor preparation. Because of the differential effects of phospholipase C and trypsin on the particulate compared with the solubilized receptor preparations, it is concluded that the effects of these enzymes were due to an effect on the surrounding membrane structure. Changes in receptor configuration due to alterations within the adjoining membrane provide a potential mechanism for mediating short-term alterations in receptor function.  (+info)

Cell surface sialic acid and the regulation of immune cell interactions: the neuraminidase effect reconsidered. (2/3160)

It has been known for over a decade that sialidase (neuraminidase) treatment could substantially enhance the capacity of resting B cells to stimulate the proliferation of allogeneic and antigen specific, syngeneic T cells. Thus, cell-surface sialic acid was implicated as a potential modulator of immune cell interaction. However, little progress has been made in either identifying explicit roles for sialic acid in this system or in hypothesizing mechanisms to explain the "neuraminidase effect." Here we show for the first time that cell surface sialic acid on medium incubated B cells blocks access to costimulatory molecules on the B cell surface, and that this is the most likely explanation for the neuraminidase effect. Further, we show that it is likely to be upregulation of ICAM-1 and its subsequent engagement of LFA-1 rather than loss of cell surface sialic acid that in part regulates access to CD86 and other costimulatory molecules. However, we cannot exclude a role for CD86-bound sialic acid on the B cell in modulating binding to T cell CD28. Because sialidase treatment of resting B cells but not resting T cells enables T cell activation, we suggest that sialidase treatment may still be an analogue for an authentic step in B cell activation, and show that for highly activated B cells (activated with polyclonal anti-IgM plus INF-gamma) there is specific loss 2, 6-linked sialic acid. Potential roles for sialic acid in modulating B cell/T cell collaboration are discussed.  (+info)

N-Linked glycosylation and sialylation of the acid-labile subunit. Role in complex formation with insulin-like growth factor (IGF)-binding protein-3 and the IGFs. (3/3160)

Over 75% of the circulating insulin-like growth factors (IGF-I and -II) are bound in 140-kDa ternary complexes with IGF-binding protein-3 (IGFBP-3) and the 84-86-kDa acid-labile subunit (ALS), a glycoprotein containing 20 kDa of carbohydrate. The ternary complexes regulate IGF availability to the tissues. Since interactions of glycoproteins can be influenced by their glycan moieties, this study aimed to determine the role of ALS glycosylation in ternary complex formation. Complete deglycosylation abolished the ability of ALS to associate with IGFBP-3. To examine this further, seven recombinant ALS mutants each lacking one of the seven glycan attachment sites were expressed in CHO cells. All the mutants bound IGFBP-3, demonstrating that this interaction is not dependent on any single glycan chain. Enzymatic desialylation of ALS caused a shift in isoelectric point from 4.5 toward 7, demonstrating a substantial contribution of anionic charge by sialic acid. Ionic interactions are known to be involved in the association between ALS and IGFBP-3. Desialylation reduced the affinity of ALS for IGFBP-3. IGF complexes by 50-80%. Since serum protein glycosylation is often modified in disease states, the dependence of IGF ternary complex formation on the glycosylation state of ALS suggests a novel mechanism for regulation of IGF bioavailability.  (+info)

Binding partners for the myelin-associated glycoprotein of N2A neuroblastoma cells. (4/3160)

The myelin-associated glycoprotein (MAG) has been proposed to be important for the integrity of myelinated axons. For a better understanding of the interactions involved in the binding of MAG to neuronal axons, we performed this study to identify the binding partners for MAG on neuronal cells. Experiments with glycosylation inhibitors revealed that sialylated N-glycans of glycoproteins represent the major binding sites for MAG on the neuroblastoma cell line N2A. From extracts of [3H]glucosamine-labelled N2A cells several glycoproteins with molecular weights between 20 and 230 kDa were affinity-precipitated using immobilised MAG. The interactions of these proteins with MAG were sialic acid-dependent and specific for MAG.  (+info)

Carbohydrate on human factor VIII/von Willebrand factor. Impairment of function by removal of specific galactose residues. (5/3160)

Human factor VIII/von Willebrand factor protein containing 120 +/- 12 nmol of sialic acid and 135 +/- 13 nmol of galactose/mg of protein was digested with neuraminidase. The affinity of native factor VIII/von Willebrand factor and its asialo form for the hepatic lectin that specifically binds asialoglycoproteins was assessed from in vitro binding experiments. Native factor VIII/von Willebrand factor exhibited negligible affinity while binding of the asialo derivative was comparable to that observed for asialo-alpha1-acid glycoprotein. Incubation of asialo-factor VIII/von Willebrand factor with Streptococcus pneumoniae beta-galactosidase removed only 62% of the galactose but abolished binding to the purified hepatic lectin. When the asialo derivative was incubated with purified beta-D-galactoside alpha2 leads to 6 sialyltransferase and CMP-[14C]NeuAc, only 61% of the galactose incorporated [14C]NeuAc. From the known specificites of these enzymes, it is concluded that galactose residues important in lectin binding are present in a terminal Gal/beta1 leads to 4GlcNAc sequence on asialo-factor VIII/von Willebrand factor. The relative ristocetin-induced platelet aggregating activity of native, asialo-, and agalacto-factor VIII/von Willebrand factor was 100:38:12, respectively, while procoagulant activity was 100:100:103.  (+info)

Tandem amino acid repeats from Trypanosoma cruzi shed antigens increase the half-life of proteins in blood. (6/3160)

Proteins containing amino acid repeats are widespread among protozoan parasites. It has been suggested that these repetitive structures act as immunomodulators, but other functional aspects may be of primary importance. We have recently suggested that tandem repeats present in Trypanosoma cruzi trans-sialidase stabilize the catalytic activity in blood. Because the parasite releases trans-sialidase, this delayed clearance of the enzyme might have implications in vivo. In the present work, the ability of repetitive units from different T. cruzi molecules in stabilizing trans-sialidase activity in blood was evaluated. It is shown that repeats present on T. cruzi shed proteins (antigens 13 and Shed-Acute-Phase-Antigen [SAPA]) increase trans-sialidase half-life in blood from 7 to almost 35 hours. Conversely, those repeats present in intracellular T. cruzi proteins only increase the enzyme half-life in blood up to 15 hours. Despite these results, comparative analysis of structural and catalytic properties of both groups of chimeric enzymes show no substantial differences. Interestingly, antigens 13 and SAPA also increase the persistence in blood of chimeric glutathione S-transferases, thus suggesting that this effect is inherent to these repeats and independent of the carrier protein. Although the molecular basis of this phenomenon is still uncertain, its biotechnological potential can be envisaged.  (+info)

Amino acid substitutions in a conserved region in the stalk of the Newcastle disease virus HN glycoprotein spike impair its neuraminidase activity in the globular domain. (7/3160)

The ectodomain of the paramyxovirus haemagglutinin-neuraminidase (HN) glycoprotein spike can be divided into two regions: a membrane-proximal, stalk-like structure and a terminal globular domain. The latter contains all the antibody recognition sites of the protein, as well as its receptor recognition and neuraminidase (NA) active sites. These two activities of the protein can be separated by monoclonal antibody functional inhibition studies and mutations in the globular domain. Herein, we show that mutation of several conserved residues in the stalk of the Newcastle disease virus HN protein markedly decrease its NA activity without a significant effect on receptor recognition. Thus, mutations in the stalk, distant from the NA active site in the globular domain, can also separate attachment and NA. These results add to an increasing body of evidence that the NA activity of this protein is dependent on an intact stalk structure.  (+info)

Ortho- and paramyxoviruses from migrating feral ducks: characterization of a new group of influenza A viruses. (8/3160)

Ortho- and parainfluenza viruses isolated from the cloacas of migrating feral ducks shot on the Mississippi flyway included three strains of influenza. A virus (Hav6 Nav1, Hav6 Nl, Hav7 Neq2) as well as Newcastle disease virus. One influenza virus, A/duck/Memphis/546/74, possessed Hav3 haemagglutinin, but the neuraminidase was not inhibited by any of the known influenza reference antisera. The neuraminidase on this virus was related to the neuraminidases on A/duck/GDR/72 (H2 N?), A/turkey/Ontario/7732/66 (Hav 5 N?), A/duck/Ukraine/1/60 (Hav3 N?) and A/turkey/Wisconsin/68. We therefore propose that the neuraminidase on this group of influenza viruses be designated Nav6. The A/duck/Memphis/546/74 influenza virus caused an ocular discharge in 1 of 5 ducks and was shed in faeces for 10 days; it was stable in faecal samples for up to 3 days at 20 degrees C. These results suggest that ecological studies on influenza in avian species should include attempts to isolate virus from faeces. Faecal-oral transmission is an attractive explanation for the spread of influenza virus from feral birds to other animals.  (+info)

  • Neuraminidases, also called sialidases, catalyze the hydrolysis of terminal sialic acid residues from the newly formed virions and from the host cell receptors. (wikipedia.org)
  • Sialic acid 3 is now more often called N-acetyl neuraminic acid , and hence the name of RDE was changed yet again, this time to neuraminidase. (everything2.com)
  • There are two major classes of Neuraminidase that cleave exo or endo poly-sialic acids: Exo hydrolysis of α-(2→3)-, α-(2→6)-, α-(2→8)-glycosidic linkages of terminal sialic acid residues Endo hydrolysis of (2→8)-α-sialosyl linkages in oligo- or poly(sialic) acids Neuraminidases, also called sialidases, catalyze the hydrolysis of terminal sialic acid residues from the newly formed virions and from the host cell receptors. (wikipedia.org)
  • α2-3,6,8 Neuraminidase catalyzes the hydrolysis of α2-3, α2-6, and α2-8 linked sialic acid residues from glycoproteins and oligosaccharides. (neb.com)
  • Parainfluenza virus type 3 hemagglutinin-neuraminidase is expressed by HPIV paramyxoviruses that bind to sialic acid-containing receptor molecules on the surface of host lung cells. (functionalglycomics.org)
  • The current strategy for treating influenza focuses on inhibiting the function of neuraminidase, which is an enveloped enzyme located on the surface of both influenza A and B. Influenza neuraminidase is an exosialidase that recognizes the α -ketosidic linkage between neuraminic acid (or sialic acid) and carbohydrate residues ( Von Itzstein, 2011 ). (peerj.com)
  • The main function of influenza neuraminidase (NA) involves enzymatic cleavage of sialic acid from the surface of host cells resulting in the release of the newly produced virions from infected cells, as well as aiding the movement of virions through sialylated mucus present in the respiratory tract. (hku.hk)
  • Our objectives were then to investigate both sialic acid binding and cleavage of neuraminidase at an atomic resolution level. (hku.hk)
  • Neuraminidase digestion abolished WGA binding to the proximal ciliary membrane surface, indicating that sialic acids mediate WGA binding to this domain. (arvojournals.org)
  • Neuraminidases are enzymes that cleave sialic acid groups from glycoproteins. (sinobiological.com)
  • Neuraminidase, on the other hand, cleaves the HA-sialic acid bondage from the newly formed virions and the host cell receptors during budding. (sinobiological.com)
  • Neuraminidase removes terminal sialic acid residues from glycoproteins. (roche.com)
  • Here, we describe a mutation in IAV nucleoprotein (NP) that enhances replication and transmission in guinea pigs while selectively reducing neuraminidase (NA) gene segment packaging into virions. (pnas.org)
  • The sequence of the cloned neuraminidase gene (nan A), was compared to other bacterial neuraminidases to identify conserved residues, and also utilising crystallography data, predictions were made of the residues likely to be important in catalysis. (bl.uk)
  • Cloning and expression of the Bacteroides fragilis TAL2480 neuraminidase gene, nanH, in Escherichia coli. (asm.org)
  • We have cloned the Bacteroides fragilis TAL2480 neuraminidase (NANase) structural gene, nanH, in Escherichia coli. (asm.org)
  • Here, we assessed the ability of a novel dual-specific anti-tumor oncolytic adenovirus, expressing the hemagglutinin-neuraminidase (HN) gene from the Newcastle disease virus under the human telomerase reverse transcriptase (hTERT) promoter (Ad-hTERTp-E1a-HN), to inhibit esophageal cancer EC-109 cells in culture and to reduce tumor burden in xenografted BALB/c nude mice. (mdpi.com)
  • Streptococcus pneumoniae is believed to produce more than one form of neuraminidase, but there has been uncertainty as to whether this is due to posttranslational modification of a single gene product or the existence of more than one neuraminidase-encoding gene. (asm.org)
  • Only one stable pneumococcal neuraminidase gene (designated nanA) has been described. (asm.org)
  • In the present study, we isolated and characterized a second neuraminidase gene (designated nanB), which is located close to nanA on the pneumococcal chromosome (approximately 4.5kb downstream). (asm.org)
  • A gene from Streptococcus pneumoniae (nanA), with features entirely consistent with a neuraminidase gene, has been sequenced. (asm.org)
  • High levels of neuraminidase activity were obtained after cloning of this gene, without flanking sequences, into a high-expression vector. (asm.org)
  • The nanH structural gene for neuraminidase was cloned from B. fragilis TM4000 and was used to create two isogenic strains with chromosomal disruptions at the nanH gene. (asm.org)
  • The Trypanosoma cruzi neuraminidase contains sequences similar to bacterial neuraminidases, YWTD repeats of the low density lipoprotein receptor, and type III modules of fibronectin. (rupress.org)
  • NanA contains the four copies of the sequence SXDXGXTW that is present in all the bacterial neuraminidases previously described. (asm.org)
  • Dynamic range of four orders of magnitude enables you to quantitate virus isolates over a broad range of virus concentration and with varying levels of neuraminidase activity without performing numerous sample dilutions. (thermofisher.com)
  • Trypanosoma cruzi expresses a developmentally regulated neuraminidase (TCNA) implicated in parasite invasion of cells. (rupress.org)
  • Antibodies which inhibit the enzyme limit the infection, but antigenic variation of the neuraminidase renders it ineffective in a vaccine. (nih.gov)
  • Escape mutants, selected by growing virus in the presence of monoclonal antibodies to the neuraminidase, possess single amino acid sequence changes. (nih.gov)
  • We have studied the maturation of the influenza A virus neuraminidase (NA), using monoclonal antibodies (MAbs) with different conformational specificities against the head domains of the N8 NA. (asm.org)
  • The wide range of reactivity probably relates to the infection history of the donor, whose plasmablasts generated antibodies with long regions that insert into the active site of the neuraminidase enzyme. (flutrackers.com)
  • We describe three human monoclonal antibodies isolated from an H3N2-infected donor that bind with exceptional breadth to multiple different influenza A and B virus neuraminidases. (flutrackers.com)
  • These antibodies neutralize the virus, mediate effector functions, are broadly protective in vivo, and inhibit neuraminidase activity by directly binding to the active site. (flutrackers.com)
  • Structural and functional characterization of these antibodies will inform the development of neuraminidase-based universal vaccines against influenza virus. (flutrackers.com)
  • Swiss-Prot lists 137 types of neuraminidase from various species as of October 18, 2006. (wikipedia.org)
  • Three types of neuraminidase are found in mammals and are defined as lysosomal, plasma membrane and cytosolic on the basis of their biochemical properties and subcellular distribution. (acris-antibodies.com)
  • The protective effects of the mutated neuraminidases in mice was investigated by immunization followed by challenge with virulent Streptococcus penumoniae. (bl.uk)
  • The specific neuraminidase activity of infective trypomastigotes obtained from tissue culture and from the bloodstream of infected mice is 7 to 15 times higher than that of the acellular culture forms. (sciencemag.org)
  • This study did not evaluate specific neuraminidase inhibitors. (lasvegasemr.com)
  • However, they displayed cumulative mutations in and around the linear epitope of hemagglutinin-neuraminidase (residues 345 to 353) with time. (asm.org)
  • Neuraminidase is an important deglycosylation enzyme capable of cleaving all non-reducing unbranched N-acetylneuraminic and N-glycolylneuraminic acid residues by hydrolysis of α (2→6), α (2→3), α (2→8), and α (2→9) linkages (affinity in the order given). (creative-enzymes.com)
  • Two fold dilutions of α2-3,6,8 Neuraminidase are incubated with 1 nmol AMC-labeled substrate and 1X GlycoBuffer 1 in a 10 µl reaction. (neb.com)
  • S. Herlambang and R. Saleh, "The Comparison of Substrate Stability in Neuraminidase Type 2 (N2) Active Site between A/Tokyo/3/67 and A/Pennsylvania/10218/84 with Heating Dynamics Simulation," World Journal of Condensed Matter Physics , Vol. 1 No. 3, 2011, pp. 77-87. (scirp.org)
  • The PNAS was designed and manufactured to quantitatively identify the levels of neuraminidase in the sample, which is based on colorimetric analysis using the X-Neu5Ac substrate. (koreascience.or.kr)
  • We have investigated the mechanism and activity of the human neuraminidase (NEU) isoenzyme, NEU3, on T cell adhesion receptors. (frontiersin.org)
  • Successful heat inactivation coincided with the loss of hemagglutinin (HA) and neuraminidase (NA) characteristics, and β-propiolactone inactivation reduced the hemagglutination titer and NA activity of the human influenza virus 10-fold or more. (asm.org)
  • Brain tissue is especially rich in membrane-bound neuraminidase which reaches its highest specific activity in the plasma membranes isolated from synaptosomes (2, 3). (springer.com)
  • The human pathogen Trypanosoma cruzi (Y strain) contains a neuraminidase activity that varies widely in the different developmental stages of the parasite. (sciencemag.org)
  • Neuraminidase shows normal activity even in the presence of 1% BME, and 0.5% SDS. (neb.com)
  • Two Bacteroides fragilis neuraminidase-deficient mutants were used to study the role of neuraminidase activity in growth of B. fragilis in tissue culture monolayers (CHO cells) and in the in vivo rat granuloma pouch. (asm.org)
  • We suggest that neuraminidase activity may be required for B. fragilis to grow to maximal levels in the tissue culture and rat pouch systems by making other carbon sources available after glucose levels are reduced. (asm.org)
  • Meanwhile, SJS targeted on neuraminidase of influenza virus as SJS at 2 mg/ml inhibited 80% of neuraminidase enzymatic activity. (biomedcentral.com)
  • 1,2 These compounds were designed to interfere with the activity of the neuraminidase enzyme of the influenza virus based on knowledge of the three-dimensional crystal structure of the enzyme, determined by Australian scientists, and of the chemistry of its interaction with cell surface receptors. (health.gov.au)
  • Model showed that electrostatic and steric interactions play important role in determining neuraminidase inhibitory activity. (jbsdonline.com)
  • A DNA sequence encoding the Influenza A virus (A/Anhui/1/2013(H7N9)) Neuraminidase (translated amino acids of EPI439509) (His36-Leu465) was expressed , the cell lysates are collected, and bio-activity was tested. (sinobiological.com)