Diacylglycerol kinase that converts diacylglycerol/DAG into phosphatidic acid/phosphatidate/PA and regulates the respective levels of these two bioactive lipids (PubMed:12883552). 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:12883552). Also plays an important role in the biosynthesis of complex lipids (Probable). 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 (PubMed:12883552). 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 (PubMed:27739494). 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 (PubMed:27739494). Found in a ternary complex with IRS1 and PIP5K1A in the absence of insulin (PubMed:27739494). Interacts with PIP5K1A (By similarity). 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. Homozygous knockout mice are viable, fertile and do not display overt phenotype (PubMed:12883552). Slight perturbations of the cellular composition of secondary lymphoid organs with a slight decrease of mature T cells is observed (PubMed:12883552). Upon TCR activation the normal conversion of diacylglycerol into phosphatidic acid that negatively regulates TCR signaling is partially impaired (PubMed:12883552). Hyper proliferation of T-cells and the ability to mount a more vigorous and effective T-cell response against pathogens indicate a more profound T-cell activation in these mice (PubMed:12883552). Belongs to the eukaryotic diacylglycerol kinase family.