The binding of microorganisms to platelets is a critical step in the development of infective endocarditis. In Streptococcus gordonii, this binding is mediated in part by serine-rich repeat proteins, which interact directly with sialic acid residues located on GPIIb receptors in the platelet membrane. In this study, we found that S. gordonii DL1 strain binds to platelets through bridging between sialic acid residue of fibronectin and serine-rich repeat protein (Hsa). Pretreatment of fibronectin with sialidases specific for alpha(2-3)-linked sialic acids was shown to significantly inhibit binding of the DL1 strain and the binding region(BR) of Hsa protein. Similarly, pre-incubation of bacteria or BR of Hsa with alpha(2-3)-sialyl-N-acetyllactosamine blocked fibronectin binding in the DL1 strain, but not the M99 strain. Together, these data show that the alpha(2-3)-sialic acid residues of fibronectin play an important role in the binding of S. gordonii DL1 to fibronectin through interactions with the Hsa receptor. This interaction is thought to play an important role in the development of pathogenic endocarditis, and may represent an important therapeutic target for the treatment of infective endocarditis.
Bacteria ; Blood Platelets ; Endocarditis ; Etorphine ; Fibronectins* ; Membrane Glycoproteins* ; Membranes ; N-Acetylneuraminic Acid* ; Sialic Acids ; Streptococcus gordonii*

Neuraminidase (NA) cleaves the glycosidic bond linkages of sialic acids to release the mature virions from infected cells and has been an attractive therapeutic target for anti-influenza agents. In our ongoing investigation of NA inhibitors in mushroom extracts, we found that the extract the fruiting body of Glaziella splendens potently inhibited neuraminidase. The fruiting bodies of G. splendens were extracted and partitioned successively with hexane, ethyl acetate, and butanol. The ethyl acetate soluble-layer was subjected to silica gel and Sephadex LH-20 column chromatographies, and MPLC to obtain five compounds (1–5). Their structures were determined by spectroscopic methods. NA inhibitory activity of these compounds was evaluated using NAs from recombinant rvH1N1, H3N2, and H5N1 influenza A viruses. One compound (1) was elucidated as a new azaphilone derivative, and four compounds (2–5) were identified as entonaemin A, comazaphilone D, rubiginosin A, and entonaemin B, respectively. Compounds 3 and 4 showed considerable inhibitory activity against three types of neuraminidases with the IC₅₀ values of 30.9, 41.8, and 35.7 µM for 3 and 46.5, 50.4, and 29.9 µM for 4, respectively. This study reveals that the fruiting bodies of G. splendens possess azaphilone derivatives with the NA inhibitory activity. This is the first report on the isolation of neuraminidase inhibitors from the fruiting bodies of G. splendens.
Agaricales ; Chromatography ; Fruit ; Influenza A virus ; N-Acetylneuraminic Acid ; Neuraminidase ; Sialic Acids ; Silica Gel ; Virion

To investigate the effects of genistein (Gen) on the biosynthesis of N-glycolylneuraminic acid (Neu5Gc) in rats, 80 4-week-old male SD rats were randomly equally into the control and genistein groups. The rats of control and genistein groups were fed 5% ethanol and 300 mg/(kg·d) genistein respectively by gavage. The contents of Neu5Gc in hind leg muscle, kidney and liver tissues of rats were measured by using high performance liquid chromatography coupled with fluorescence detector (HPLC/FLD), and the mechanism of inhibition of Neu5Gc synthesis was investigated by using the molecular docking of Gen and sialyltransferase. On the 15th day, the content of Neu5Gc in hind leg muscle and liver tissues decreased 13.77% and 15.45%, respectively, and there was no significant change in the content of Neu5Gc in kidney tissues. On the 30th day, the content of Neu5Gc in liver tissues decreased 13.35%, however, there was no significant change in the content of Neu5Gc in kidney tissues and Neu5Gc was not detected in hind leg muscle. The content of Neu5Gc in hind leg muscle, kidney and liver tissues decreased respectively 32.65%, 32.78%, 16.80% and 12.72%, 11.42%, 12.30% while rats fed on the 45th and the 60th days. Genistein has formed the hydrogen bond with sialyltransferase activity site residues His319, Ser151, Gly293, Thr328 and formed a hydrophobic interactions with the residues His302, His301, Trp300, Ser271, Phe292, Thr328, Ser325 and Ile274. The results of molecular docking indicated that the weak intermolecular interaction was the main cause of genistein inhibiting sialyltransferase activity. The research results provided an experimental basis for the subsequent reduction of Neu5Gc in red meat before slaughter.
Animals ; Gene Expression Regulation, Enzymologic ; drug effects ; Genistein ; pharmacology ; Male ; Molecular Docking Simulation ; Neuraminic Acids ; metabolism ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Transferases ; metabolism

In comparison with its counterpart from N. meningitides, all conserved motifs were found in the N-termini of E. coli CMP-NeuAc synthetase. E. coli CMP-NeuAc synthetase seems to have redundant C-termini with a less effect on its activity. To explain this speculation, a series of recombinant DNAs with deletion from 3'-end of CMP-NeuAc synthetase were produced by PCR, ligated into expression vector pET-15b and expressed in BL21(DE3)pLysS. After induction with IPTG, we found that the recombinant enzyme with deletion of 189 amino acids from C0termini retained its activity. This result demonstrates that the 229 amino acids of N-termini was the minimal functional domain of E. coli CMP-NeuAc synthetase. The deletions altered the optimum pH and thermostability of active truncated enzymes, indicating that the truncated C-terminal amino acids of E. coli CMP-NeuAc synthetase could affect the conformation of the enzymatic catalytic domain and therefore affect its catalytic activity and thermostability, although it is not involved in enzymatic activity directly.
Amino Acid Sequence ; Cytidine Monophosphate N-Acetylneuraminic Acid ; metabolism ; Enzyme Stability ; Escherichia coli ; enzymology ; Hydrogen-Ion Concentration ; Molecular Sequence Data ; Mutation ; N-Acylneuraminate Cytidylyltransferase ; chemistry ; physiology ; Structure-Activity Relationship

BACKGROUND: Sialic acid residues are known to play a key role in the normal function of the glycoconjugates. Recently, with the development of specific sialic acid binding lectins such as Maackia seed agglutinin(MAA) and Sambucus nigra agglutinin(SNA), it has made easier to localize the sialic acid residues by the histochemical staining methods. OBJECTIVES: We were to observe the expression of sialic acids according to the differentiation of cultured human nasal epithelial cells by the immunohistochemistry method using Wheat germ agglutinin(WGA), MAA, and SNA. MATERIALS AND METHODS: Human nasal epithelial cell culture was done as floating method for the induction of differentiation. The cultured cells were fixed with 2.5% glutaraldehyde and the epon 812 was used as embedding material. The immunohistochemistry was done as Lim's method. RESULTS: The WGA and MAA positive reactions were noted from the floating zero day through the fourteenth day. The reactions were positive to the squamous-like cells and differentiating cells(ciliated and secretory epithelial cells). The WGA binding patterns were homogeneous but MAA binding patterns were inhomogeneous. The SNA positive reaction was noted only in the fourteenth day and the reaction was inhomogeneous. These results meant that N-acetyl glucosamine and N-acetyl neuraminic acid(alpha 2,3) galactose were expressed from the floating zero day and N-acetyl neuraminic acid(alpha 2,6) galactose was expressed from the floating fourteenth day. CONCLUSION: N-acetyl neuraminic acid(alpha 2,3) galactose may be more important to the primary defence of human nasal epithelial cell. Due to the inhomogeneity of the reaction, the further study using Lowicryl K4M will be needed.
Cells, Cultured ; Epithelial Cells* ; Galactose ; Glucosamine ; Glutaral ; Glycoconjugates ; Humans* ; Immunohistochemistry ; Lectins ; Maackia ; N-Acetylneuraminic Acid* ; Sambucus nigra ; Sialic Acids* ; Triticum

Adamantane ; therapeutic use ; Amantadine ; therapeutic use ; Antiviral Agents ; therapeutic use ; Child ; Guanidines ; Humans ; Influenza, Human ; drug therapy ; prevention & control ; Pyrans ; Rimantadine ; therapeutic use ; Sialic Acids ; therapeutic use ; Zanamivir

Lectins are proteins responsible for recognizing the signals of sugar molecules in the body. Sialic acid-binding immunoglobulin-like lectins (Siglecs) regulate the innate and adaptive immune responses in the tumor microenvironment by recognizing the glycan structure containing sialic acid and mediating downstream signals through immune receptor tyrosine inhibitory motifs. In recent years, a variety of tumor treatment strategies targeting the sialic acid-Siglecs axis have been introduced, including sialoglycoprotein-mediated drug delivery and antibody mediated inhibition of Siglecs from recognizing tumor surface ligands. In the future, by combining with glycoprotein nanotherapy, antibody therapy and gene therapy, Siglecs can be used to accurately locate tumor targets and release the anti-tumor immunity, so as to achieve the purpose of effective cure of tumors.
Sialic Acid Binding Immunoglobulin-like Lectins/metabolism* ; N-Acetylneuraminic Acid ; Immunoglobulins/metabolism* ; Receptors, Immunologic ; Ligands

BACKGROUND: GNE myopathy is characterized by early-adult-onset distal myopathy sparing quadriceps caused by mutations in the GNE gene encoding UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase, an enzyme in the sialic-acid synthesis pathway. CASE REPORT: A 27-year-old Korean woman presented a rapid deterioration in strength of the distal lower limbs during her first pregnancy. She was diagnosed with GNE myopathy and carrying the compound heterozygous mutations of the GNE gene (D208N/M29T). CONCLUSIONS: This is a representative case implying that an increased requirement of sialic acid during pregnancy might trigger a clinical worsening of GNE myopathy.
Adult ; Distal Myopathies ; Female ; Humans ; Lifting ; Lower Extremity ; Muscular Diseases* ; N-Acetylneuraminic Acid ; Phosphotransferases ; Pregnancy*

Bacillus subtilis is recognized as a generally-regarded-as-safe strain, and has been widely used in the biosynthesis of high value-added products, including N-acetylneuraminic acid (NeuAc) which is widely used as a nutraceutical and a pharmaceutical intermediate. Biosensors responding to target products are widely used in dynamic regulation and high-throughput screening in metabolic engineering to improve the efficiency of biosynthesis. However, B. subtilis lacks biosensors that can efficiently respond to NeuAc. This study first tested and optimized the transport capacity of NeuAc transporters, and obtained a series of strains with different transport capacities for testing NeuAc-responsive biosensors. Subsequently, the binding site sequence of Bbr_NanR responding to NeuAc was inserted into different sites of the constitutive promoter of B. subtilis, and active hybrid promoters were obtained. Next, by introducing and optimizing the expression of Bbr_NanR in B. subtilis with NeuAc transport capacity, we obtained an NeuAc-responsive biosensor with wide dynamic range and higher activation fold. Among them, P535-N2 can sensitively respond to changes in intracellular NeuAc concentration, with the largest dynamic range (180-20 245) AU/OD. P566-N2 shows a 122-fold of activation, which is 2 times of the reported NeuAc-responsive biosensor in B. subtilis. The NeuAc-responsive biosensor developed in this study can be used to screen enzyme mutants and B. subtilis strains with high NeuAc production efficiency, providing an efficient and sensitive analysis and regulation tool for biosynthesis of NeuAc in B. subtilis.
N-Acetylneuraminic Acid/metabolism* ; Bacillus subtilis/metabolism* ; Promoter Regions, Genetic/genetics* ; Binding Sites ; Biosensing Techniques

A boy, aged 3 hours, was admitted due to a prenatal diagnosis of fetal hydrops at 3 hours after resuscitation for birth asphyxia. Prenatal examination at 5 months of gestation showed massive ascites in the fetus, and after birth, the boy had the manifestations of systemic hydroderma, massive ascites, coarse face, and hepatomegaly. Genetic testing revealed heterozygous mutations in the SLC17A5 gene, and there was a significant increase in urinary free sialic acid. Placental pathology showed extensive vacuolization in villous stromal cells, Hofbauer cells, cytotrophoblast cells, and syncytiotrophoblast cells in human placental chorionic villi. The boy was finally diagnosed with free sialic acid storage disorders (FSASDs). This is the first case of FSASDs with the initial symptom of fetal hydrops reported in China. The possibility of FSASDs should be considered for cases with non-immune hydrops fetalis, and examinations such as placental pathology and urinary free sialic acid may help with early diagnosis and clinical decision making.
Infant, Newborn ; Male ; Humans ; Female ; Pregnancy ; Hydrops Fetalis/genetics* ; N-Acetylneuraminic Acid ; Placenta/pathology* ; Ascites