Catalyzes a base-exchange reaction in which the polar head group of phosphatidylethanolamine (PE) or phosphatidylcholine (PC) is replaced by L-serine (PubMed:19014349). Catalyzes the conversion of phosphatatidylethanolamine and does not act on phosphatidylcholine (PubMed:19014349). 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 Requires calcium ions (PubMed:19014349). Inhibited by exogenous phosphatidylserine (PubMed:19014349). Optimum pH is around 7.5. Phospholipid metabolism; phosphatidylserine biosynthesis. Highly enriched in the mitochondria-associated membrane (MAM). Belongs to the phosphatidyl serine synthase family.