title: Substrate specificity and inhibitor studies of a membrane-bound ganglioside sialidase isolated from human brain tissue.
abstract: A ganglioside-specific sialidase that controls cellular functions such as growth, differentiation, and adhesion has been observed in a variety of cells, but its characterization proved difficult due to firm membrane attachment and lability of the purified enzyme. Here we report on the specificity toward gangliosides and susceptibility to certain inhibitors of a ganglioside sialidase solubilized and purified 5100-fold from human brain. The sialidase removed terminal sialic acids from gangliosides GM3, GM4, GD3, GD2, GD1 a, GD1 b, GT1 b and GQ1 b, but was inactive toward gangliosides with sialic acid in a branching position (as in GM1 and GM2). Lyso-GM3 and -GD1a were good substrates, too, whereas O-acetylation of the sialic acid as in 9-O-acetyl-GD3 caused strongly reduced cleavage. The new influenza virus drug 4-guanidino-2-deoxy-2,3-dehydro-N-acetylneuraminic acid (Zanamivir) exhibited an IC50 value of about 7 x 10(-5) M that was in the range of the 'classical' sialidase inhibitor 2-deoxy-2,3-dehydro-N-acetylneuraminic acid; the bacterial sialidase inhibitor 4-nitrophenyloxamic acid, however, was ineffective. The glycosaminoglycans heparan sulfate, heparin, chondroitin sulfates A and B, as well as dextran sulfate and suramin, were all strongly inhibitory, suggesting that glycosaminoglycans present on the cell surface or in the extracellular matrix may influence the ability of the sialidase to alter the ganglioside composition of the membrane.
authors.affiliation: Institute of Pathochemistry and Neurochemistry, University of Heidelberg, Im Neuenheimer Feld 220/221, D-69120 Heidelberg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Oehler
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kopitz
authors.forename: Michael
authors.initials: M
authors.lastname: Cantz
mesh_terms: D000918:Antibody Specificity; D015153:Blotting, Western; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D002462:Cell Membrane / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D000939:Epitopes / Q000276:immunology; D005732:Gangliosides / Q000378:metabolism; D006025:Glycosaminoglycans / Q000494:pharmacology; D006493:Heparin / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D019216:Metals, Heavy / Q000494:pharmacology; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D009439:Neuraminidase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D013379:Substrate Specificity; D013431:Sulfates / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D000939:Epitopes; D005732:Gangliosides; D006025:Glycosaminoglycans; D019216:Metals, Heavy; D013431:Sulfates; D006493:Heparin; C036052:GM3 ganglioside sialidase; D009439:Neuraminidase; D019158:N-Acetylneuraminic Acid