A plasma membrane-associated phospholipase in SV40-transformed 3T3 cells

Cells of a SV3T3 line can be adapted to degrade phosphatides made into a film. A phosphatide degrading enzyme(s) was localized at cell surface structures by cytochemistry. Biochemistry of cell fractions indicated the presence of a phospholipase which was bound to the plasma membrane. It has a substrate specificity for phosphatidylserine, a pH optimum in the acid region, and is inhibited by calcium. It is not dissociated from the membrane by products of phospholipid degradation and is presumably a phospholipase A. The hydrolysis of the substrate under experimental conditions is about 32%. The cell biological importance of the enzyme is discussed in regard to cellular interactions and invasiveness of virus-transformed cells.