Enables CDP-diacylglycerol-serine O-phosphatidyltransferase activity and L-serine-phosphatidylethanolamine phosphatidyltransferase activity. Acts upstream of or within phosphatidylserine biosynthetic process. Located in endoplasmic reticulum membrane. Is expressed in several structures, including heart; hemolymphoid system; liver; nervous system; and testis. Orthologous to human PTDSS2 (phosphatidylserine synthase 2). [provided by Alliance of Genome Resources, Apr 2022]