Diacylglycerol kinase that converts diacylglycerol/DAG into phosphatidic acid/phosphatidate/PA and regulates the respective levels of these two bioactive lipids (PubMed:12200442, 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 (Probable). By controlling the levels of diacylglycerol, regulates for instance the PKC and EGF receptor signaling pathways and plays a crucial role during development (By similarity). May also regulate clathrin-dependent endocytosis (PubMed:17880279). {ECO:0000250|UniProtKB:E9PUQ8, ECO:0000269|PubMed:12200442, ECO:0000269|PubMed:17880279, ECO:0000269|PubMed:23949095, ECO:0000305}. This is the function of Ensembl gene identifier ENSG00000077044 (DGKD, diacylglycerol kinase delta).