Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.53 (sialidase)
 2,694 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A zonal rotor technique for the preparation of synaptosomes in bulk from bovine brain frontal cortex based on an impirical transformation of a small-volume discontinuous sucrose density gradient arrangement is presented in detail. The procedure yields new information concerning synaptosomes prepared in sucrose gradients. Cerebroside analysis and electron microscopy show myelin contamination to be restricted to the leading, less dense edge of the synaptosomal profile, free mitochondria to the trailing, more dense edge. Exclusion of fringe areas yields a highly purified synaptosome preparation which entirely enters the next dense layer beyond the 0.8 : 1.2 M sucrose interface. This interface collects most of the oubain-sensitive (Na+, K+) adenosine triphosphatase activity. The purified synaptosomes display very high intrinsic sialidase activity and are rich in di-, tri-, and tetrasialogangliosides, the preferred substrates for the enzyme. Up to 90% of the cholinesterase activity in the zonal rotor synaptosome preparation is specific acetylcholinesterase.
 ...
PMID:Large-scale preparation of synaptosomes from bovine brain using a zonal rotor technique. 15 41

Removal of sialic acid from intact mammalian nervous system cells in tissue culture is accompanied by an immediate increase in cellular cholinesterase activity. Treatment of hamster astroblast cells (clonal line NN) and mouse neuroblastoma cells (clonal lines S21, N18, and N115) for brief periods with a low level of Clostridium perfringens sialidase, 5 X 10(-3) units/ml, removed 1-15 mug of sialic acid per mg of cell protein and brought about a large increase in v0 and Vmax of cellular acetylcholinesterase (EC 3.1.1.7). Butyrylcholinesterase (EC 3.1.1.8) activities also increased upon careful enzymatic removal of cellular sialic acid, and cells with characteristically low butyrylcholinesterase activity, e.g., adrenergic clonal line N115 neuroblasts displayed relatively high activity after treatment with sialidase. These findings open the possibility that adaptive regulation of cholinesterases in mammalian cells may be mediated rapidly through changes in their sialic acid content.
 ...
PMID:Activation of acetyl- and butyrylcholinesterase by enzymatic removal of sialic acid from intact neuroblastoma and astroblastoma cells in culture. 17 21

Sialate 9(4)-O-acetylesterases (EC 3.1.1.53) have been isolated from equine liver, bovine brain and influenza C virus. In this latter case, the esterase represents the receptor-destroying enzyme of the virus. The kinetic properties of these enzymes were determined with Neu5,9Ac2 and in part with 4-methylumbelliferyl acetate and Neu5,9Ac2-lactose. The Km values vary between 0.13 and 24 mM and the Vmax values from 0.55 to 11 U/mg of protein. The pH optima are in the range of 7.4-8.5, the molecular masses at 56,500 and 88,000 Da. In addition to a fast hydrolysis found for aromatic acetates, such as 4-methylumbelliferyl acetate or 4-nitrophenyl acetate, N-acetyl-9-O-acetylneuraminic acid is de-O-acetylated at the highest relative rate. Other substituents at the 9-position, such as lactoyl residues, or acetyl groups at other positions within the side chain are not hydrolyzed. Neu4,5Ac2, however, is a substrate for all 3 enzymes. The hydrolysis rates of this ester function, which renders sialic acids resistant to the action of sialidases, vary from 3 to 100% relative to Neu5,9Ac2. Whereas Neu5,9Ac2-lactose is hydrolyzed by the bovine and viral esterases, other O-acetylated sialic acids in glycoconjugates are only attacked by the enzyme from influenza C virus and not by that from bovine brain. The esterase from horse liver also releases 4-O-acetyl groups from equine submandibular gland mucin. By incubation with appropriate substrates and inhibition studies, carboxylesterase, amidase and choline esterase activities were excluded, as well as the cleavage of other acyls, e.g., butyryl groups. Thus, the enzymes investigated belong to the acetylesterases.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Sialate O-acetylesterases: key enzymes in sialic acid catabolism. 314 20

Glycosylphosphatidylinositol (GPI)-anchored proteins are ubiquitous in eukaryotes. The minimum conserved GPI core structure of all GPI-anchored glycans has been determined as EtN-PO4-6Manalpha1-2Manalpha1-6Manalpha1-4GlcN-myo-inositol-PO3H. Human placental alkaline phosphatase (AP) has been reported to be a GPI-anchored membrane protein. AP carries one N-glycan, (NeuAcalpha2-->3)2Gal2GlcNAc2Man3GlcNAc(+/-Fuc)GlcNAc, and a GPI anchor, which contains an ethanolamine phosphate diester group, as a side chain. However, we found that both sialidase-treated soluble AP (sAP) and its GPI-anchored glycan bound to a Psathyrella velutina lectin (PVL)-Sepharose column, which binds beta-GlcNAc residues. PVL binding of asialo-sAP and its GPI-anchored glycan was diminished by digestion with diplococcal beta-N-acetylhexosaminidase or by mild acid treatment. After sequential digestion of asialo-sAP with beta-N-acetylhexosaminidase and acid phosphatase, the elution patterns on chromatofocusing gels were changed in accordance with the negative charges of phosphate residues. Trypsin-digested sAP was analyzed by liquid chromatography/electrospray ionization mass spectrometry, and the structures of two glycopeptides with GPI-anchored glycans were confirmed as peptide-EtN-PO4-6Manalpha1-->2(GlcNAcbeta1-PO4-->6)Manalpha1-6(+/-EtN-PO4-->)Manalpha1-->4GlcN, which may be produced by endo-alpha-glucosaminidase. In addition to AP, GPI-anchored carcinoembryonic antigen, cholinesterase, and Tamm-Horsfall glycoprotein also bound to a PVL-Sepharose column, suggesting that the beta-N-acetylglucosaminyl phosphate diester residue is widely distributed in human GPI-anchored glycans. Furthermore, we found that the beta-N-acetylglucosaminyl phosphate diester residue is important for GPI anchor recognition of aerolysin, a channel-forming toxin derived from Aeromonas hydrophila.
 ...
PMID:A beta-N-acetylglucosaminyl phosphate diester residue is attached to the glycosylphosphatidylinositol anchor of human placental alkaline phosphatase: a target of the channel-forming toxin aerolysin. 1285 98