Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.1.53 (sialidase)
2,694 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ultrastructural cytochemistry of the alveolar-capillary "membrane" has been investigated. Dialyzed iron and high iron diamine staining demonstrated a layer containing sulfated mucosubstance at the basal surface of the membranous pneumocytes. In the same layer, fixation with an osmium tetroxide-potassium pyroantimonate solution yielded abundant fine precipitates which were abolished by inclusion of ehtylene glycol bis-N,N'-tetraacetic acid (EGTA) in the fixative. This cation-retaining layer could be interpreted as providing a mechanism for retarding cation transport from the basement membrane to the alveolar space. High iron diamine staining also demonstrated a layer of sulfated mucosubstance on the microvilli of the granular pneumocytes. This layer corresponded with a sialidase-resistant, dialyzed iron-reactive stratum which overlaid the sialomucin-rich cell coat.
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PMID:A cation-retaining layer in the alveolar-capillary membrane. 6 17

Gastric and intestinal phenotypic expression in 37 surgically obtained primary signet ring cell carcinomas, five of their metastases to lymph nodes, and three signet ring cell carcinomas transplanted into nude mice were determined by biochemical, mucin, histochemical, and ultrastructural studies. Crude extracts of cancer tissues were used for measurements of pepsinogen isozymes, sucrase, aminopeptidase (microsomal), and alkaline phosphatase. Histochemical staining of mucin by paradoxical concanavalin A, the galactose oxidase-Schiff sequence and sialidase-galactose oxidase-Schiff, and the periodate-borohydride technique/potassium hydroxide/periodic acid-Schiff procedure was performed. The procedures allowed clear definition of pyloric gland, surface mucous, small and large intestinal goblet, and intestinal absorptive cell types. Of 40 specimens examined, 19 consisted entirely of gastric-type cells, and three entirely of intestinal-type cells. The others consisted of mixtures of gastric and intestinal-type cells. The observed high incidence of intestinal-type cells in signet ring cell carcinomas suggested that intestinal-type cells develop independently from intestinal metaplasia within signet ring cell carcinomas (diffuse-type gastric cancers), which probably originate from nonmetaplastic gastric mucosa.
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PMID:Gastric and intestinal phenotypic expressions of human signet ring cell carcinomas revealed by their biochemistry, mucin histochemistry, and ultrastructure. 301

The components of periodontal connective tissue were studied on days 28-30 after replantation of the teeth with the extra-alveolar time 5, 15, and 30 min. The levels of collagen, glucosaminoglycanes, sialic acids, and activity of sialidase increased at extra-alveolar time 30 min by 44, 33, and 20, and 85%, respectively. Introduction of potassium hyaluronate in dental wells reduced the sail collagen growth in the periodontal tissue.
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PMID:[Periodontal function after replantation]. 773 48

Cell surface carbohydrates have been shown to be altered during cellular differentiation. Alveolar type II (ATII) cells in culture gradually lose their differentiated phenotype. Therefore, the aim of this study was: (1) to characterize changes in terminal carbohydrates of cell surface glycoproteins of rat ATII cells cultured for 1 to 5 days on plastic, and (2) to assess the concomitant changes in sialidase and sialyltransferase activity of ATII cell homogenates. Cells were surface-labeled with potassium-[3H]-borohydride after oxidation by sodium periodate at millimolar concentrations, galactose oxidase or neuraminidase plus galactose oxidase, allowing for the specific labeling of terminal sialic acids, terminal galactose/N-acetylgalactosamine (Gal/GalNAc), or terminal an penultimate Gal/GalNAc residues, respectively. Glycoproteins were separated by SDS-PAGE. On day 1, cells were heavily coated with sialic acids, since no labeling could be introduced with galactose oxidase alone. From day 1 to day 5, we observed a selective and progressive desialylation of two glycoproteins (200 and 165 kD). At the same time, the ATII cells' sialidase activity (pH 4.2) exhibited an 8-fold increase (60.3 +/- 4.0 pmol/min/mg protein on day 1 versus 406.9 +/- 3.7 pmol/min/mg protein on day 5), whereas the sialyltransferase activity increased 2-fold (212 +/- 8 fmol/min/mg protein on day 1 versus 395 +/- 82 fmol/min/mg protein on day 5) and the supernatant sialidase activity was unchanged (2.8 +/- 0.7 pmol/min/ml on day 5). Thus, the phenotypic changes of ATII cells in primary culture are accompanied by a partial cell surface desialylation and an increase in intracellular sialidase activity.
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PMID:Cell surface carbohydrates of rat alveolar type II cells in primary culture. 842 6

Kv1.1 potassium (K+) channels contain significant amounts of negatively charged sialic acids. To examine the role of sialidation in K+ channel function, Chinese hamster ovary cell lines deficient in glycosylation (Lec mutants) were transfected with rat brain Kv1.1 cDNA. The K+ channel was functionally expressed in all cell lines, but the voltage dependence of activation (V1/2) was shifted to more positive voltages and the activation kinetics were slower in the mutant cell lines compared with control. A similar positive shift in V1/2 was recorded in control cells expressing Kv1.1 following treatment with sialidase or by raising extracellular Ca2+. In contrast, these treatments had little or no effect on the Lec mutants, which indicates that channel sialic acids appear to be the negative surface charges sensitive to Ca2+. The data suggest that sialic acid addition modifies Kv1.1 channel function, possibly by influencing the local electric field detected by its voltage sensor, but that these carbohydrates are not required for cell surface expression.
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PMID:Expression of Kv1.1 delayed rectifier potassium channels in Lec mutant Chinese hamster ovary cell lines reveals a role for sialidation in channel function. 870 82

Sections from the major salivary glands of rats and mice were used to locate, characterize and compare sialoglycoconjugates by means of lectin histochemistry, sialidase digestion, periodate oxidation and potassium hydroxide deacetylation. The gland sialylated macromolecules contained the terminal dimers sialic acid-beta-galactose and sialic acid-alpha-N-acetyl-galactosamine but differed in the varieties of sialic acids and the linkages of sialic acids to penultimate sugars. Indeed, the submandibular and parotid glands exhibited a notable occurrence of periodate labile sialic acids with C7 and/or C8 and/or C9 acetyl groups in their polyhydroxyl chains. In particular, C9 acetylated sialic acids were mostly linked alpha 2-6 to beta-galactose. The sublingual glands, instead, were strongly characterized by a presence of C9 acetylated sialic acids bound alpha 2-3 to beta-galactose. Also, sialic acids with O-acetyl substituents at C4 were evident in the mouse parotid gland and in the rat submandibular and sublingual glands. The great variety of sialoderivatives expressed by the rodent salivary glands was correlated with the differential involvement of these compounds in lubricating and defensive processes. Sex-related differences regarding the sialic acid location, acetylation degree and linkage were shown in the submandibular glands of both species.
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PMID:Histoenzymological detection of sialic acids in the rodent salivary glands. 883 55

Capitalizing on the readily available ganglioside, GM1, we have devised a simple synthesis of labeled GM1 analogues with sulfur in place of oxygen in their linkage to the ceramide residue (SGM1). The sugar moiety of ganglioside GM1 was released by ozonolysis and subsequent alkaline fragmentation in good yield. During acetylation of the ganglioside sugar, the carboxyl group of the sialic acid residue lactonized with the 2-hydroxyl group of the inner galactose moiety (galactose II). The resulting sialoyl-II2-lactone of pentadeca-O-acetyl-monosialogangliotetraose could be readily transformed into the alpha-glycosyl bromide. Subsequent treatment of this glycosyl bromide with potassium thioacetate afforded the sialoyl-II2-lactone of tetradeca-O-acetyl-1-S-acetyl-1-thio-beta-monosialogangliotetra ose. The latter could be condensed with (2R, 3R, 4E)-3-O-benzoyl-2-dichloroacetamido-1-iodo-4-octadecen -3-ol in methanolic sodium acetate to afford a protected lyso-SGM1 derivative. One-step removal of the protecting groups under alkaline conditions gave beta-monosialogangliotetraosyl thiosphingosine. This lyso-SGM1 was converted into labeled analogues of SGM1 using the N-succinimidoyl derivative of radiocarbon-labeled octanoic and octadecanoic acid, respectively. Subsequent actions of GM1-beta-galactosidase, beta-hexosaminidase A, sialidase and again GM1-beta-galactosidase on these labeled analogues of SGM1 in the presence of taurodeoxycholate produced the respective analogues of GM2, GM3, lactosylceramide and glucosylceramide, respectively.
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PMID:Synthesis of ganglioside GM1 containing a thioglycosidic bond to its labeled ceramide(s). A facile synthesis starting from natural gangliosides. 940 93

Sialic acids from the liver and serum of guinea-pig are composed of N-acetylneuraminic acid (Neu5Ac; 85% and 61%, respectively), N-acetyl-4-O-acetylneuraminic acid (Neu4,5Ac2; 10% and 32%, respectively) and N-glycolylneuraminic acid (Neu5Gc; 5% and 7%, respectively), besides traces of N-glycolyl-4-O-acetylneuraminic acid in serum. The analysis was carried out using thin-layer chromatography, high-performance liquid chromatography, electron impact ionization mass spectrometry, and different enzymes (sialidase, sialate esterase, and sialate-pyruvate lyase after hydrolysis and purification of the sialic acids by ion-exchange chromatography). We showed that this O-acetylation of sialic acids is due to the activity of an acetyl-coenzyme A:sialate-4-O-acetyltransferase (EC 2.3.1.44), which occurs together with sialyltransferase activity in Golgi-enriched membrane fractions of guinea-pig liver. The enzyme operates optimally at 30 degrees C in 70 mM potassium phosphate buffer at pH 6.7 and in the presence of 90 mM KCI with an apparent KM for AcCoA of 0.6 1microM and a Vmax of 20 pmol/mg protein x min. The enzyme is inhibited by coenzyme A in a mixed-competitive manner (Ki = 4.2 microM), as well as by parachloromercuribenzoate, MnCl2, saponin and Triton X-100.
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PMID:Enzymatic 4-O-acetylation of N-acetylneuraminic acid in guinea-pig liver. 1005 93

The testes of prepubertal and adult horses were investigated using 10 horseradish peroxidase conjugated lectins combined with sialidase digestion and potassium hydroxide treatment, to localise the oligosaccharide sequences of glycoconjugates during spermatid maturation. In adult animals, the lectins showed a variable affinity for spermatids and Sertoli cell apical extensions. Soybean agglutinin (SBA), peanut agglutinin (PNA), Ricinus communis agglutinin (RCA-I) and wheat germ agglutinin (WGA) bound to the acrosomal structures of spermatids, whereas Griffonia simplicifolia agglutinin (GSA-II) labelled these structures only during Golgi and cap phases. These results suggested that glycoproteins of mature acrosomes contain both N- and O-linked oligosaccharides and that these carbohydrate chains undergo modifications during spermiogenesis. Sialic acid residues were not detected throughout the acrosomal development. The lectin binding pattern of Sertoli cells was very similar to that of acrosome of spermatids during the maturation phase. In sexually immature horses, only the degenerated germinal cells and the Leydig cells showed reactivity towards lectins. The first cells reacted with SBA and Dolichos biflorus agglutinin (DBA), the latter with SBA, PNA, WGA, GSA-II, Canavalia ensiformis agglutinin (ConA), Lens culinaris agglutinin (LCA) and also with DBA after sialidase digestion.
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PMID:Localization of the lectin reactive sites in adult and prepubertal horse testes. 1102 Mar 60

The growing interest in glycoconjugates expressed and released by the epithelium of the intestinal mucosa is tightly related to the multiple functional roles attributed to sialic acid and its derivatives. In the present work, biotin and HRP conjugated lectins were used to detect the sialylation pattern and to identify specific structural features of sialoderivatives in the rat colon. In particular, the occurrence and distribution of sialic acids linked alpha2,6 to D-Gal/D-GalNAc and alpha2,3 to D-Gal were directly demonstrated with SNA and MAL II binding, respectively. In addition, in order to by-pass the specificity problems of SNA and MAL II as histochemical reagents, as well as to look for additional and complementary information about acetylation degree and sites, we combined sialidase digestion, potassium hydroxide deacetylation, and differential periodate oxidation with PNA and DBA binding. The data showed the distribution and structure of sialic acid-beta-D-Gal(1-3)-D-GalNAc and sialic acid-D-GalNac sequences, which proved to be widely distributed as cellular components or secretory products in surface goblet cells and crypt cells of the colonic epithelium. A high degree of O-acetylation, with acetyl groups mainly at 9 and 4 positions, was found, showing an increasing gradient from the proximal to distal portion of the colon. These results, which largely reproduce the sialylation pattern in other species, contribute new insights in defining the tissue specific expression of sialoderivatives in the colonic mucosa, and testify to their high heterogeneity which the wide range of sialic acid functional correlates in the intestinal tract depend on.
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PMID:Lectin histochemistry for in situ profiling of rat colon sialoglycoconjugates. 1843 85


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