Diacylglycerol kinase (DGK) alpha enhances the proliferation of melanoma and hepatocellular carcinoma cells whereas, in contrast, DGK alpha induces a nonproliferative state in T cells. We previously found that DGK alpha produces palmitic acid (16:0)-containing PA species, such as 16:0/16:0- and 16:0/18:0-PA, in melanoma cells under serum-starved (nonproliferative) conditions. In the present study, we identified the PA species generated by DGK alpha in T cells under serum-starved (nonproliferative) conditions. We found that serum starvation markedly increased the levels of many PA species, such as 14:1/16:1-, 14:0/16:1-, 14:0/16:0-, 16:1/16:2-, 16:1/16:1-, 16:0/16:1-, 16:0/16:0-, 16:1/18:2-, 16:1/18:1-, 16:0/18:1-, 16:0/18:0-, 18:1/18:2-, 18:1/18:1- and 18:0/18:1-PA, in Jurkat T cells. In lysates from serum-starved Jurkat T cells, DGK alpha activity, which was Ca2+-dependent and sensitive to a DGK alpha-specific inhibitor (CU-3), was substantially increased, indicating its activation. Moreover, CU-3 (1-10 mM) significantly reduced the amounts of palmitic acid- and/or palmitoleic acid (16:1)-containing PA species, such as 14:1/16:1-, 14:0/ 16:1-, 14:0/16:0-, 16:1/16:2-, 16:1/16:1-, 16:0/16:1-, 16:0/16:0-, 16:0/18:1- and 16:0/18:0-PA, which were increased by serum starvation. These results indicate that DGKa generates different PA species in starved melanoma cells (palmitic acid-containing PA species) and T cells (palmitic acid- and/or palmitoleic acid (16:1)-containing PA species). Therefore, the differences in the PA molecular species may account for the opposing functions of DGKa in melanoma and T cells. (C) 2020 Elsevier Inc. All rights reserved.