The protein encoded by this gene catalyzes the formation of phosphatidylserine from either phosphatidylcholine or phosphatidylethanolamine. Phosphatidylserine localizes to the mitochondria-associated membrane of the endoplasmic reticulum, where it serves a structural role as well as a signaling role. Defects in this gene are a cause of Lenz-Majewski hyperostotic dwarfism. Two transcript variants encoding different isoforms have been found for this gene.,PTDSS1,LMHD,PSS1,PSSA,Cancer,Signal Transduction,Endocrine & Metabolism,Lipid Metabolism,PTDSS1