Diacylglycerol kinase that converts diacylglycerol/DAG into phosphatidic acid/phosphatidate/PA and regulates the respective levels of these two bioactive lipids (PubMed:9159104, PubMed:15544348, PubMed:18004883, PubMed:19744926, PubMed:22108654, PubMed:22627129, PubMed:23949095). 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:9159104, PubMed:15544348, PubMed:18004883, PubMed:19744926, PubMed:22108654, PubMed:22627129, PubMed:23949095). Also plays an important role in the biosynthesis of complex lipids (Probable). Does not exhibit an acyl chain-dependent substrate specificity among diacylglycerol species (PubMed:9159104, PubMed:19744926, PubMed:22108654). Can also phosphorylate 1-alkyl-2-acylglycerol in vitro but less efficiently and with a preference for alkylacylglycerols containing an arachidonoyl group (PubMed:15544348, PubMed:19744926, PubMed:22627129). 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 (PubMed:15157668). Through the same mechanism could also positively regulate insulin-induced translocation of SLC2A4 to the cell membrane (By similarity). Regulates RASGRP1 activity. Does not regulate RASGRP1 activity. 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(+) Activated by 1,2-diacyl-sn-glycero-3-phosphate/phosphatidic acid irrespective of its acyl chain composition. Lipid metabolism; glycerolipid metabolism. Interacts (via PDZ-binding motif) with the PDZ domain of the syntrophin SNTG1 and that of SNX27 (PubMed:11352924, PubMed:17351151). 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. Highest levels in brain, and substantial levels in skeletal muscle, heart, and pancreas. Predominantly expressed in muscle. The PDZ-binding motif mediates interaction with PDZ domain-containing proteins like SNTG1 and SNX27. Phosphorylation of the MARCKS homology domain by PKC reduces nuclear accumulation of DGK-zeta. Minor isoform. Major isoform. Belongs to the eukaryotic diacylglycerol kinase family.