Diacylglycerol kinase that converts diacylglycerol/DAG into phosphatidic acid/phosphatidate/PA and regulates the respective levels of these two bioactive lipids. Thereby, acts as a central switch between the signaling pathways activated by these second messengers with different cellular targets and opposite effects in numerous biological processes. Also plays an important role in the biosynthesis of complex lipids. a 1,2-diacyl-sn-glycerol + ATP = a 1,2-diacyl-sn-glycero-3-phosphate + ADP + H(+) Optimum pH is 7.0 with 1,2-dioctanoyl-sn-glycerol as a substrate, and 7.4 with 1,2-dihexanoyl-sn-glycerol as a substrate. Lipid metabolism; glycerolipid metabolism. Monomer. Expressed at low level during vegetative growth and during early development. Higher levels of expression are detected later during development (12-24 hours). Belongs to the eukaryotic diacylglycerol kinase family. The initially described myosin heavy chain kinase activity is probably artifactual due to numerous errors in the sequence used for characterization.