Catalyzes a base-exchange reaction in which the polar head group of phosphatidylethanolamine (PE) or phosphatidylcholine (PC) is replaced by L-serine (PubMed:12912985, PubMed:9235902). Catalyzes the conversion of phosphatatidylethanolamine and does not act on phosphatidylcholine (PubMed:12912985, PubMed:9235902). Shows a substrate specificity for phosphatatidylethanolamine and does not act on phosphatidylcholine (By similarity). Can utilize both phosphatidylethanolamine (PE) plasmalogen and diacyl PE as substrate and the latter is six times better utilized, indicating the importance of an ester linkage at the sn-1 position (By similarity). Although it shows no sn-1 fatty acyl preference, exhibits significant preference towards docosahexaenoic acid (22:6n-3) compared with 18:1 or 20:4 at the sn-2 position (By similarity). a 1,2-diacyl-sn-glycero-3-phosphoethanolamine + L-serine = a 1,2-diacyl-sn-glycero-3-phospho-L-serine + ethanolamine 1-hexadecanoyl-2-(9Z-octadecenoyl)-sn-glycero-3-phosphoethanolamine + L-serine = 1-hexadecanoyl-2-(9Z-octadecenoyl)-sn-glycero-3-phospho-L-serine + ethanolamine 1-hexadecanoyl-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-sn-glycero-3-phosphoethanolamine + L-serine = 1-hexadecanoyl-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-sn-glycero-3-phosphoserine + ethanolamine 1-octadecanoyl-2-(5Z,8Z,11Z,14Z)-eicosatetraenoyl-sn-glycero-3-phosphoethanolamine + L-serine = 1-octadecanoyl-2-(5Z,8Z,11Z,14Z)-eicosatetraenoyl-sn-glycero-3-phosphoserine + ethanolamine 1-octadecanoyl-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-sn-glycero-3-phosphoethanolamine + L-serine = 1-octadecanoyl-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-sn-glycero-3-phosphoserine + ethanolamine 1-(1Z-octadecenyl)-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-sn-glycero-3-phosphoethanolamine + L-serine = 1-(1Z-octadecenyl)-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-sn-glycero-3-phospho-L-serine + ethanolamine 1-octadecanoyl-2-(9Z-octadecenoyl)-sn-glycero-3-phosphoethanolamine + L-serine = 1-octadecanoyl-2-(9Z-octadecenoyl)-sn-glycero-3-phospho-L-serine + ethanolamine 1-(1Z-octadecenyl)-2-(9Z-octadecenoyl)-sn-glycero-3-phosphoethanolamine + L-serine = 1-(1Z-octadecenyl)-2-(9Z-octadecenoyl)-sn-glycero-3-phospho-L-serine + ethanolamine 1-(1Z-octadecenyl)-2-(5Z,8Z,11Z,14Z- eicosatetraenoyl)-sn-glycero-3-phosphoethanolamine + L-serine = 1-(1Z-octadecenyl)-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phospho-L-serine + ethanolamine Inhibited by excess phosphatidylserine, but not by phosphatidylcholine nor phosphatidylethanolamine. Phospholipid metabolism; phosphatidylserine biosynthesis. Highly enriched in the mitochondria-associated membrane (MAM). Belongs to the phosphatidyl serine synthase family.