Microanalytical determination of the activities of phospholipases A, C, and D and of their mixtures

In the course of studies on the catabolite repression of succinate dehydrogenase in yeast (1), the need arose to monitor simultaneously phospholipases A and D activities in broken cell preparations. Although a variety of assay methods are described in the literature for both of these enzymes, none of them appeared to provide a simple and unambiguous measure of both activities simultaneously at the very low enzyme concentrations and with the crude enzyme preparations used. Therefore, a method was developed, based on the use of uniformly labeled ¹⁴C-lecithin, which provides simple and relatively easy assays for phospholipases A, C, and D, as well as for mixtures of the three enzymes, and permits initial-rate measurements. Details are described in this paper. Comparison of the methods described with other assays for phospholipases is presented in the Discussion.