Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A procedure was devised for the preparation of enriched populations of subcellular organelles from homogenized bovine spleen. The fractions obtained were characterized for arylsulfatase, succinate dehydrogenase, UDPgalactosyltransferase and 5'-nucleotidase activities. The distribution of sialidase (acylneuraminyl hydrolase, EC 3.2.1.18) activity directed towards either endogenous substrate or exogenous ganglioside substrate suggests that it is enriched in the plasma membrane/microsomal fractions. Sialidase activity towards exogenous sialoglycoproteins, isolated from erythrocyte membrane, was enriched in the least dense of the plasma membrane/microsomal-containing fractions. The endogenous sialidase substrates were primarily the sialoglycolipids, hematoside and disialogangliosides. At the pH optimum, 3.8, and 37 degrees C, release of endogenous sialic acid was linear with time for 3 h. At the end of this time, 85% or more of the available endogenous substrate was hydrolyzed.
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PMID:Distribution in spleen subcellular organelles of sialidase active towards natural sialogylcolipid and sialoglycoprotein substrates. 48 91

A rapid small-scale procedure was set up to obtain highly purified preparations of lysosomes and plasma membranes from the homogenate of cerebellar granule cells differentiated in culture. It consisted in a centrifugation of the postnuclear fraction P2, on a Percoll gradient with formation of an upper and lower band. The upper band, upon centrifugation on 1 M sucrose, produced a light band lying on the top, that constituted the plasma membrane preparation. The upper band constituted the lysosome preparation. The plasma membrane preparation exhibited a 6-fold relative specific activity increase of Na+, K(+)-ATPase and 5'-nucleotidase, with negligible contamination by other subcellular markers; the lysosomal preparation exhibited a 30-fold relative specific activity increase of beta-galactosidase and beta-hexosaminidase, with virtually no contamination by other subcellular markers. Both the lysosome and plasma membrane preparations carried sialidase activity on MUB-NeuNAc and ganglioside GD1a. The sialidase activity on GD1a required the presence of Triton X-100 in both subcellular preparations; the sialidase activity on MUB-NeuNAc was markedly activated by albumin only in the lysosomes. The lysosomal sialidase had a unique optimal pH value, 3.9. The plasma membrane sialidase featured two values of optimal pH, one at 3.9, for both substrates and second at 5.4 and 6.0 for MUB-NeuNAc and GD1a, respectively. It is concluded that cerebellar granule cells differentiated in vitro possess one lysosomal sialidase and two plasma membrane sialidases, all of them active on ganglioside.
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PMID:Dual subcellular localization of sialidase in cultured granule cells differentiated in culture. 130 62

The total pellet from pig forebrain (from which the cytosolic sialidase was completely washed out) was treated with phosphatidylinositol phospholipase C (PIPLC) and centrifuged at high speed. The supernatant contained sialidase and 5'-nucleotidase activities. The greatest liberation of sialidase was obtained after incubation for 20 min with PIPLC at 37 degrees C using pH 6.0 and a ratio between PIPLC (as units) and protein of 1.6. Under these conditions, the release of sialidase, 5'-nucleotidase, and protein was 22, 50, and 18.5%, respectively. On treatment with PIPLC, a purified preparation of pig brain neuronal (synaptosomal) membranes released 28% of its sialidase whereas a purified preparation of pig brain lysosomes did not liberate any sialidase activity. The pH optimum of sialidase present in the supernatant obtained after PIPLC treatment of the total pellet was 4.2, the same as that of the enzyme embedded in the membrane. When this supernatant was subjected to ammonium sulfate fractionation, 88% of its sialidase, having a pH optimum of 4.2, was recovered in the fraction precipitated between 20 and 45% of salt saturation and subsequently dialyzed. Ammonium sulfate treatment caused the appearance of a second sialidase activity, having a pH optimum of 6.6 and behaving on fractionation similarly to the pH 4.2 sialidase. The Km and Vmax values of pH 4.2 and pH 6.6 sialidase were similar (1.48 x 10(-4) and 0.98 x 10(-4) M for Km and 1.6 and 1.4 mU/mg of protein for Vmax, respectively), whereas the stability on standing at 4 degrees C or exposure to freezing and thawing cycles was greater for pH 4.2 sialidase.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Solubilization of the membrane-bound sialidase from pig brain by treatment with bacterial phosphatidylinositol phospholipase C. 221 10