Diacylglycerol kinase that converts diacylglycerol/DAG into phosphatidic acid/phosphatidate/PA and regulates the respective levels of these two bioactive lipids (PubMed:17021016). 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 (PubMed:17021016). By controlling the levels of diacylglycerol, regulates for instance the PKC and EGF receptor signaling pathways and plays a crucial role during development (PubMed:17021016). May also regulate clathrin-dependent endocytosis (By similarity). a 1,2-diacyl-sn-glycerol + ATP = a 1,2-diacyl-sn-glycero-3-phosphate + ADP + H(+) 1,2-di-(9Z-octadecenoyl)-sn-glycerol + ATP = 1,2-di-(9Z-octadecenoyl)-sn-glycero-3-phosphate + ADP + H(+) 1-octadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycerol + ATP = 1-octadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphate + ADP + H(+) Lipid metabolism; glycerolipid metabolism. Homooligomer. Monomer. Interacts with AP2A2; regulates clathrin-dependent endocytosis. Widely expressed. The SAM domain mediates homooligomerization. The PH domain mediates association with membranes. Homozygous knockout of dgkd is lethal (PubMed:17021016). Fetuses are smaller and newborn mice develop respiratory difficulty and die within 24 hours after birth (PubMed:17021016). They show an abnormal open-eyelids phenotype which is associated with significant reduction of the expression of the EGF receptor/EGFR in the basal layer of the epidermis (PubMed:17021016). Belongs to the eukaryotic diacylglycerol kinase family.