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)

Aiming at the introduction of a fluorescent sialic acid into glycoconjugates, 5-acetamido-9-(3-fluoresceinylthio-ureido)-3,5,9-trideoxy-2-non ulosonic acid (9-fluoresceinyl-NeuAc) was synthesized which has an intact carbon chain. a) Despite the space-filling substituent at C-9, the fluorescent NeuAc analogue was activated to the corresponding CMP-glycoside by CMP sialic acid synthase from bovine brain. Whereas the Km value of the synthase was little affected by the modification (Km = 2.1 mM, for NeuAc Km = 1.4 mM), the V value decreased to 7.5%. b) CMP-9-fluoresceinyl-NeuAc was synthesized on a preparative scale (17% overall yield), and characterized by analytical HPLC, absorption and fluorescence spectra. c) 9-Fluoresceinyl-NeuAc was transferred onto asialo-alpha 1-acid glycoprotein by both Gal beta 1, 4GlcNAc alpha 2, 6sialyltransferase and Gal beta 1,4(3)GlcNAc alpha 2,3sialyltransferase (rat liver), and onto antifreeze glycoprotein by GalNAc alpha 2,6-sialyltransferase (porcine submaxillary glands). Using analytical HPLC, transfer was confirmed after release of the fluorescent sialic acid by Vibrio cholerae sialidase. d) Initial rate studies indicated a low Km value of Gal beta-1,4GlcNAc alpha 2,6sialyltransferase, and GalNAc alpha 2,6sialyltransferase (specific for O-linked oligosaccharide chains) for CMP-9-fluoresceinyl-NeuAc.
 ...
PMID:Enzymatic introduction of a fluorescent sialic acid into oligosaccharide chains of glycoproteins. 284 3

In spite of the axially orientated hydroxy group at C-4, the benzyl alpha-glycoside of N-acetyl-4-epi-D-neuraminic acid (4-epi-NeuAc) is a substrate for sialidases from Vibrio cholerae, Clostridium perfringens, and Arthrobacter ureafaciens, although to an extent which differs depending on the enzyme. Surprisingly, V. cholerae sialidase is by far the slowest acting enzyme; this is in contrast to its usual behavior. Fowl plague virus sialidase and bovine testis sialidase also cleave this glycoside slowly. 4-Epi-NeuAc is not a substrate for N-acetylneuraminic acid aldolase from C. perfringens but reversibly inhibits the enzyme with a Ki = 2.3 mM. The N-acetylneuraminic acid analogue is not converted to the corresponding CMP-glycoside by CMP-sialic acid synthase from bovine brain; however, it is an effective reversible inhibitor of the enzyme. The kinetic properties were analyzed with an assay system at pH 9 as well as an assay system at pH 7.5. The results from Dixon and Hanes plots did not agree. Therefore, no conclusions about the mechanism of the inhibition could be reached. This is the first reported sialic acid analogue which can act as an inhibitor of CMP-sialic acid synthase.
 ...
PMID:Interaction of N-acetyl-4-epi-D-neuraminic acid with key enzymes of sialic acid metabolism. 316 79

The activities of ten enzymes involved in sialic acid metabolism were measured in colonic mucosal cells from rats and compared with those in liver. A methodology was devised that enabled all ten enzyme activities to be evaluated in a single rat colon preparation. Enzyme assays with radioactively labelled substrates were developed for maximum sensitivity, and the identification of substrates and products was carefully checked to assess the contribution of contaminants to enzyme reactions with low activity. The activities of most enzymes involved in the biosynthesis of N-acetyl-D-neuraminic acid (NeuAc) from UDP-N-acetyl-D-glucosamine were found to be more than 20-fold lower than those in liver. The activities of CMP-NeuAc synthase, N-acetyl-D-glucosamine 2-epimerase, N-acetyl-D-glucosamine kinase, sialyltransferase and sialidase were similar to or 2-4-fold lower than in liver. The biosynthesis of NeuAc via its 9-phosphate was demonstrated in the 100 000 g supernatant of colonic-cell homogenates by enzymic assay and precursor experiments with N-acetyl[14C]-mannosamine. No alternative route for NeuAc formation could be detected. The 100 000g supernatant fractions of liver, kidney and colonic mucosal cells utilized N-acetyl[14C]mannosamine with differing efficiencies. Radioactive products identified as sialic acid biosynthetic intermediates amounted to 49%, 0.04% and 5.6% of added precursor in liver, kidney and colon respectively. Catabolism of labelled precursor to non-hexosamine products was high in kidney and colonic mucosal-cell fractions.
 ...
PMID:The metabolism of sialic acids in isolated rat colonic mucosal cells. 397 62