Dual substrate-specific glycerol-3-phosphate/dihydroxyacetone phosphate sn-1 acyltransferase, catalyzing the first and committed reaction in the de novo synthesis of glycerophospholipids and triacylglycerols (TAGs). Prefers Gly-3-P over dihydroxyacetone phosphate and has a marked preference for 16-carbon fatty acyl chains. Transfers a fatty acid from fatty acyl-CoA to the sn-1 position of glycerol-3-phosphate to produce lysophosphatidic acid (LysoPA). These lipids not only are precursors of glycerolipids, but also are dynamic components of signal transduction systems that control cell physiology (PubMed:11544256). SCT1 is the primary supplier of diacylglycerols (DAG), used mainly in TAG synthesis and phosphatidylcholine (PC) synthesis through the CDP-choline pathway (PubMed:12167660). Regulates fatty acid desaturation, that is, the ratio of unsaturated versus saturated fatty acyl chains, by competing with the desaturase OLE1 for the common substrate C16:0-CoA. Sequesters C16:0-CoA into lipids, thereby shielding it from desaturation by OLE1 (PubMed:22323296). an acyl-CoA + sn-glycerol 3-phosphate = a 1-acyl-sn-glycero-3-phosphate + CoA an acyl-CoA + dihydroxyacetone phosphate = a 1-acylglycerone 3-phosphate + CoA hexadecanoyl-CoA + sn-glycerol 3-phosphate = 1-hexadecanoyl-sn-glycero-3-phosphate + CoA (9Z)-hexadecenoyl-CoA + sn-glycerol 3-phosphate = 1-(9Z-hexadecenoyl)-sn-glycero-3-phosphate + CoA octadecanoyl-CoA + sn-glycerol 3-phosphate = 1-octadecanoyl-sn-glycero-3-phosphate + CoA (9Z)-octadecenoyl-CoA + sn-glycerol 3-phosphate = 1-(9Z-octadecenoyl)-sn-glycero-3-phosphate + CoA Phospholipid metabolism; CDP-diacylglycerol biosynthesis; CDP-diacylglycerol from sn-glycerol 3-phosphate: step 1/3. Localizes to both perinuclear and cortical endoplasmic reticulum. The HXXXXD motif is essential for acyltransferase activity and may constitute the binding site for the phosphate moiety of the glycerol-3-phosphate. Present with 1050 molecules/cell in log phase SD medium. Belongs to the GPAT/DAPAT family.