The presence of phospholipids and diglyceride kinase activity in microtubules from different tissues

Microtubular preparations obtained by different procedures from chick embryonic muscles and brains and from HeLa cells have associated, in addition to the protein kinase which can phosphorylate tubulin, an enzymatic activity which has been identified as that of a diglyceride kinase. They have also consistently associated various phospholipids, lecithin being the principal one. The phosphatidic acid formation is greatly stimulated by exogenous diglycerides or pretreatment with phospholipase C, and it is not present in partially purified preparations of cytoplasmic protein kinases of chick muscle. The significance of these findings is discussed.