Binding sites for horseradish peroxidase on the cell surface. Suppression of binding by gangliosides and effects of some bivalent cations.

The cytochemical reaction for surface-bound horseradish peroxidase (HRP) on cultured HeLa cells, GH3 cells, and isolated rat liver cells was suppressed by 30 microM monosialoganglioside, by 30 microM trisialoganglioside, or by 5 mM CMP-neuraminic acid. The reaction was also suppressed by 10 mM chitotriose or by 10 mM UDP-galactose, a galactose acceptor and donor, respectively, for galactosyl-transferase. The addition of 2 mM Mn2+ to the incubation medium with HRP suppressed the reaction for surface-bound HRP, and the addition of 10-20 mM Ca2+ intensified the reaction. The addition of 2 mM Zn2+ caused less inhibition than that of 2 mM Mn2+, and the addition of 2 mM Co2+ caused either a slight inhibition, or no inhibition. These observations support the hypothesis that HRP may be bound to a glycosyltransferase at the cell surface.