Phosphatidate Kinase, A Novel Enzyme in Phospholipid Metabolism (Characterization of the Enzyme from Suspension-Cultured Catharanthus roseus Cells)

摘要: Phosphatidate kinase (adenosine 5[prime]-triphosphate:phosphatidic acid phosphotransferase), a novel enzyme of phospholipid metabolism, was detected recently in the plasma membranes suspension-cultured Catharanthus roseus cells and purified (J.B. Wissing, H. Behrbohm [1993] Plant Physiol 102: 1243–1249). In present work properties phosphatidate are described. The showed pH optimum 6.1 an isoelectric point 4.8, rather stable presence its substrates. Although accepted both ATP GTP, with Km values about 12 18 [mu]M, respectively, only lipid substrate phosphatidic acid; neither lysophosphatidic nor any other tested phosphorylated. With 32P- 14C-labeled diacylglycerol pyrophosphate, product enzyme, it shown that catalyzes reversible reaction. activity extracted depended on surfactants such as Triton X-100 or [beta]-octylglucoside, whereas deoxycholate strongly inhibitory. Kinetic analysis X-100/phosphatidate mixed micelles performed according to “surface dilution” kinetic model saturation kinetics respect bulk surface concentration phosphatidate. interfacial Michaelis constant for determined 0.6 mol %.