Synapsins contain O-linked N-acetylglucosamine.

The neuron-specific synaptic vesicle-associated phosphoproteins synapsin I and synapsin II were shown to contain terminal N-acetylglucosamine (GlcNAc) residues as determined by specific labeling with bovine galactosyltransferase and UDP-[3H]galactose. The beta-elimination of galactosyltransferase radiolabeled synapsin I and subsequent analysis of released saccharide on high-voltage paper electrophoresis confirmed the presence of monosaccharidic GlcNAc moieties in O-linkage to the protein. Partial cleavage of synapsin I by collagenase, 2-nitro-5-thiocyanobenzoic acid, and Staphylococcus aureus V8 protease suggests that at least three glycosylation sites exist along the molecule. Taken together these data present the first evidence that a neuron-specific protein contains O-glycosidically bound GlcNAc.