The function of GPAM (glycerol-3-phosphate acyltransferase, mitochondrial, ENSG00000119927) is as follows. Mitochondrial membrane protein that catalyzes the essential first step of biosynthesis of glycerolipids such as triglycerides, phosphatidic acids and lysophosphatidic acids (PubMed:18238778, PubMed:19075029, PubMed:36522428). Esterifies acyl-group from acyl- coenzyme A (acyl-CoA) to the sn-1 position of glycerol-3-phosphate, to produce lysophosphatidic acid (PubMed:18238778). Has a narrow hydrophobic binding cleft that selects for a linear acyl chain (PubMed:36522428). Catalytic activity is higher for substrates with a 16-carbon acyl chain (PubMed:36522428). {ECO:0000269|PubMed:18238778, ECO:0000269|PubMed:19075029, ECO:0000269|PubMed:36522428}.