Effects of OK-432 activation on the sialidase activities of rat peritoneal macrophages.

Intraperitoneal treatment of rat peritoneal macrophages with OK-432 results in more than 9-fold increase in the activity of ganglioside sialidase, which seems to coincide with the appearance of a cell surface antigen, asialo-GM1. The results of subsequent studies suggest that the ganglioside sialidase is located in the plasma membrane, where the enzyme may be responsible for the formation of asialo-GM1 from GM1. In the macrophages activated with OK-432, sialidase activity toward 4-methylumbelliferyl-N-acetylneuraminic acid (4MU-NeuAc) is also increased. It appears that the 4MU-NeuAc sialidase is intralysosomal and is increased together with other acid hydrolases present in the lysosomes.