Physiological actions of phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis on KB III cells: alkaline phosphatase release and growth inhibition.

Phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis caused the release of alkaline phosphatase from KB III cells and plasma membrane preparations prepared from the cells. Phosphatidylinositol-specific phospholipase C added to the culture of KB III cells inhibited cell growth by 30%. The release of alkaline phosphatase induced by phospholipase C was dependent on, or proportional to, the reaction time and the concentrations of the phospholipase C, KB III cells and plasma membrane preparation. The Arrhenius plot for phosphatase-release reaction showed a single break at 18.1 degrees C for KB III cells or at 27.3 degrees C for the plasma membrane preparation. The activation energies of the phosphatase-release reaction were 3.2 and 29.2 kcal/mol for KB III cells, and 4.3 and 26.5 kcal/mol for the plasma membrane preparation. The released alkaline phosphatase had a mol. wt of 105,000 and isoelectric points of 4.05 (major) and 4.4 (minor).