Phosphatidylserine (PS) accounts for 5 to 10% of cell membrane phospholipids. In addition to its role as a structural component, PS is involved in cell signaling, blood coagulation, and apoptosis. PS is synthesized by a calcium-dependent base-exchange reaction catalyzed by PS synthases , like PTDSS1, that exchange L-serine for the polar head group of phosphatidylcholine (PC) or phosphatidylethanolamine (PE).

The deduced 473-amino acid protein has transmembrane domains and a putative tyrosine phosphorylation site, and it shares 97.3% identity with Chinese hamster PS synthase. Northern blot analysis detected PTDSS1 expression in all human tissues and cell lines examined, with highest levels in heart, lung, liver, and kidney.