Sialyltransferase-1 in a human malignant glioma cell line. Kinetic characteristics and effect of human interferon-beta.

Sialyltransferase-1 activity was studied in cultured 12-18 human glioma cells. The apparent Km and Vmax with variable LacCer concentrations were 32 microM and 197 pmoles/mg protein/hr and with variable CMP-NeuAc concentrations were 172 microM and 877 pmoles/mg protein/hr., respectively. The pH optimum towards exogenous LacCer was 6.0 and towards endogenous acceptors was 6.2. The optimum protein:detergent ratio was 1:1. Human beta interferon (1000 units/ml medium) increased sialyltransferase-1 activity only slightly on a protein basis but increased it 47% on a per cell basis. These results demonstrate that one of the biochemical effects of beta-interferon on 12-18 human glioma cells is to stimulate ganglioside synthesis.