Transfers an acyl-group from acyl-ACP to the sn-1 position of glycerol-3-phosphate producing a lysophosphatidic acid (LPA), an essential step for the triacylglycerol (TAG) and glycerophospholipids (PubMed:17013544, PubMed:17689486, PubMed:22905194). In vitro also transfers an acyl-group from acyl-ACP to the LPA producing a phosphatidic acid (PA) (PubMed:22905194). Prefers arachidonoyl-CoA as the acyl donor (PubMed:22905194). Required for primary processing step during piRNA biosynthesis (PubMed:23611983). Molecular mechanisms by which it promotes piRNA biosynthesis are unclear and do not involve its acyltransferase activity (PubMed:23611983). an acyl-CoA + sn-glycerol 3-phosphate = a 1-acyl-sn-glycero-3-phosphate + CoA a 1-acyl-sn-glycero-3-phosphate + an acyl-CoA = a 1,2-diacyl-sn-glycero-3-phosphate + CoA (9Z)-octadecenoyl-CoA + 1-(9Z-octadecenoyl)-sn-glycero-3-phosphate = 1,2-di-(9Z-octadecenoyl)-sn-glycero-3-phosphate + CoA (5Z,8Z,11Z,14Z)-eicosatetraenoyl-CoA + 1-(9Z-octadecenoyl)-sn-glycero-3-phosphate = 1-(9Z)-octadecenoyl-2-(5Z,8Z,11Z,14Z)-eicosatetraenoyl-sn-glycero-3-phosphate + CoA (5Z,8Z,11Z,14Z)-eicosatetraenoyl-CoA + sn-glycerol 3-phosphate = 1-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphate + CoA Inhibited by N-ethylmaleimide (NEM). Phospholipid metabolism; CDP-diacylglycerol biosynthesis; CDP-diacylglycerol from sn-glycerol 3-phosphate: step 1/3. Interacts with PIWIL2 (PubMed:23611983). Highly expressed in the testis (PubMed:26268560). Expressed at lower levels in the heart, liver, kidney, spleen and adipose cells (PubMed:17013544, PubMed:17689486). Only detected in primary spermatocytes (PubMed:22905194). Highly expressed in pachytene spermatocytes (at protein level) (PubMed:26268560). Up-regulated by retinoic acid (PubMed:26268560). The HXXXXD motif is essential for acyltransferase activity and may constitute the binding site for the phosphate moiety of the glycerol-3-phosphate. Belongs to the GPAT/DAPAT family.