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. Does not exhibit an acyl chain-dependent substrate specificity among diacylglycerol species. Can also phosphorylate 1-alkyl-2-acylglycerol in vitro but less efficiently and with a preference for alkylacylglycerols containing an arachidonoyl group (By similarity). The biological processes it is involved in include T cell activation since it negatively regulates T-cell receptor signaling which is in part mediated by diacylglycerol (By similarity). By generating phosphatidic acid, stimulates PIP5KIA activity which regulates actin polymerization (By similarity). Through the same mechanism could also positively regulate insulin-induced translocation of SLC2A4 to the cell membrane (By similarity). Regulates RASGRP1 activity (By similarity). a 1,2-diacyl-sn-glycerol + ATP = a 1,2-diacyl-sn-glycero-3-phosphate + ADP + H(+) 1,2-didecanoyl-sn-glycerol + ATP = 1,2-didecanoyl-sn-glycero-3-phosphate + ADP + H(+) 1,2-ditetradecanoyl-sn-glycerol + ATP = 1,2-ditetradecanoyl-sn-glycero-3-phosphate + ADP + H(+) 1-hexadecanoyl-2-(9Z-octadecenoyl)-sn-glycerol + ATP = 1-hexadecanoyl-2-(9Z-octadecenoyl)-sn-glycero-3-phosphate + ADP + H(+) 1-hexadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycerol + ATP = 1-hexadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphate + ADP + H(+) 1-octadecanoyl-2-(9Z-octadecenoyl)-sn-glycerol + ATP = 1-octadecanoyl-2-(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(+) 1-octadecanoyl-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-sn-glycerol + ATP = 1-octadecanoyl-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-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-(9Z-octadecenoyl)-2-hexadecanoyl-sn-glycerol + ATP = 1-(9Z)-octadecenoyl-2-hexadecanoyl-sn-glycero-3-phosphate + ADP + H(+) 1-eicosanoyl-2-(5Z,8Z,11Z,14Z)-eicosatetraenoyl-sn-glycerol + ATP = 1-eicosanoyl-2-(5Z,8Z,11Z,14Z)-eicosatetraenoyl-sn-glycero-3-phosphate + ADP + H(+) 1,2-di-(5Z,8Z,11Z,14Z)-eicosatetraenoyl-sn-glycerol + ATP = 1,2-di-(5Z,8Z,11Z,14Z)-eicosatetraenoyl-sn-glycero-3-phosphate + ADP + H(+) 1-O-alkyl-2-acyl-sn-glycerol + ATP = 1-O-alkyl-2-acyl-sn-glycero-3-phosphate + ADP + H(+) 1-O-hexadecyl-2-acetyl-sn-glycerol + ATP = 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphate + ADP + H(+) 1-O-hexadecyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycerol + ATP = 1-O-hexadecyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphate + ADP + H(+) 1-O-hexadecyl-2-(9Z-octadecenoyl)-sn-glycerol + ATP = 1-O-hexadecyl-2-(9Z-octadecenoyl)-sn-glycero-3-phosphate + ADP + H(+) 1-O-hexadecyl-sn-glycerol + ATP = 1-O-hexadecyl-sn-glycero-3-phosphate + ADP + H(+) Lipid metabolism; glycerolipid metabolism. Interacts (via PDZ-binding motif) with the PDZ domain of the syntrophin SNTG1 and that of SNX27 (By similarity). Interacts with IRS1 in the absence of insulin; insulin stimulation decreases this interaction (By similarity). Found in a ternary complex with IRS1 and PIP5K1A in the absence of insulin (By similarity). Interacts with PIP5K1A (PubMed:15157668). Forms a signaling complex with RASGRP1 and HRAS (By similarity). The PDZ-binding motif mediates interaction with PDZ domain-containing proteins like SNTG1 and SNX27. Belongs to the eukaryotic diacylglycerol kinase family.