Diacylglycerol kinase (DGK) is the enzyme which phosphorylates diacylglycerol (DG) resulting in the production of phosphatidic acid (PA). Both DG and PA are very important signaling molecules. DG regulates the activity and localization of several proteins, including protein kinase C (PKC), chimerins, Unc-13, and Ras guanyl nucleotide-releasing protein (RasGRP). PA also activates several enzymes, including phosphatidylinositol 4-phosphate 5-kinase, mammalian target of rapamycin (mTOR), and atypical isoforms of PKC. DGK is thought to be a key enzyme that regulates numerous cellular responses by regulating balance of the two lipid messengers. All DGKs have two cysteine-rich regions (C1A and C1B domains), except for DGKθ which has three regions, in the regulatory domain of the N-terminal half of the molecule. These C1 domains of DGKs are homologous to those of PKC, which shows a DG-dependent protein kinase activity. However, not all of the C1 domains but only those of DGKβ and γ show the binding activity to DG. DGKβ, γ, ?, ζ, ι, and θ are localized in neurons and DGKα is reported to be localized in oligodendrocytes, although most DGKs are abundantly expressed in brain.1.Yasuhito Shirai,et al. J Biomed Sci. 2014; 21(1): 28.