Diacylglycerol kinases (DGKs) phosphorylate diacylglycerol (DAG) to produce phosphatidic acid. DAG and phosphatidic acid are lipids that act as second messengers in signaling cascades. DGK-alpha influences cell activation and secretion of lethal exosomes, which in turn control cell death. DGK-beta is abundant in restricted brain regions such as the caudate putamen and olfactory tubercle. DGK-gamma encodes full-length and truncated transcripts that are present in a range of human tissues, with greatest expression observed in retina. DGK-delta is most abundant in skeletal muscle. DGK-E shows specificity for arachidonylcontaining diacylglycerol and is expressed predominantly in testis. DGK-0 is most abundant in the cerebellum and hippocampus. DGK-? is present in brain and retina as a predominant transcript of more than 12 kb, including a long 3-prime untranslated region, with additional low abundance transcripts of 9.5 and 7.5 kb. DGK-? is closely related to DGK-delta. DGK-? is most abundant in brain and muscle. DGKs have structural motifs that play regulatory roles, and these motifs form the basis for dividing the DGKs into five subtypes.