title: Identification of intrinsic sialidase and sialoglycoprotein substrates in rat brain synaptic junctions.
abstract: Sialidase activity associated with rat brain synaptic junctions (SJ) and synaptic membranes (SM) was determined. Both fractions released sialic acid from exogenous glycopeptides and gangliosides. SJ accounted for 5-10% of the total sialidase activity recovered from SM following extraction with Triton X-100, and the specific activity of SJ sialidase was 60% of that of the parent SM fraction. Intrinsic SJ sialidase hydrolysed 12-15% of the sialic acid associated with endogenous SJ glycoproteins. Sialic acid residues associated with SJ glycoproteins were labelled with sodium borotritide and SJ proteins fractionated by affinity chromatography on concanavalin A-agarose. SJ glycoproteins that reacted with concanavalin A (con A+ glycoproteins) accounted for 25% of the total SJ [3H]sialic acid. Intrinsic SJ sialidase hydrolysed 20% of the [3H]sialic acid associated with these glycoproteins. Each molecular weight class of con A+ glycoprotein previously shown to be a specific component of the postsynaptic apparatus contained sialic acid and was acted on by intrinsic SJ sialidase.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D008970:Molecular Weight; D009439:Neuraminidase / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012795:Sialoglycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism*; D014316:Tritium
chemical_list: D012795:Sialoglycoproteins; D014316:Tritium; D009439:Neuraminidase