Butyrate-induced glycolipid biosynthesis in HeLa cells: properties of the induced sialyltransferase.

CMP-sialic acid:lactosylceramide sialyltransferase is induced in HeLa cells by butyrate which also causes the cells to undergo morphological changes including the extension of neurite-like processes. The activity of this enzyme is more than 20-fold higher in butyrate-treated cells than in cells grown without this short chain fatty acid. In vitro synthesis of hematoside from endogenous acceptors is also elevated in cells grown in the presence of butyrate. The levels of induced enzyme activity are influenced by the pH of the culture medium, being higher in more acidic cultures, but are not affected markedly by varying the cell density over a wide range. Detergent is required for in vitro sialyltransferase activity, and this activity is stimulated almost fivefold by cardiolipid. The optimum pH for in vitro activity is 6.0 and the apparent K_m value for lactosylceramide is 3.5 × 10^?5m. Although there are several sialyltransferase activities in HeLa cells, the induced enzyme is specific for lactosylceramide.