{"id":"4aa103f1-e43a-50b8-a351-7fb92aedddbc","stable_key":"649e861b-265a-5912-bc36-3a73e53ef892:l-serine-pss1-exchange","predicate":"uses_serine_to_make","statement":"Purified human PSS1 reconstituted with phosphatidylcholine showed serine base-exchange activity producing phosphatidylserine.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"a3ee856c-7180-5d29-aca8-ad70e46dc17d","mechanism_event_label":"Serine can replace a phospholipid headgroup to make a different membrane lipid.","subject":{"id":"0b5548b5-3cd8-5f19-8eea-dfae2a671fb3","slug":"ptdss1","display_name":"Human phosphatidylserine synthase 1 / PTDSS1","entity_type_key":"protein"},"object":{"id":"0e2dd859-6135-556e-938f-d177f1e8c1ad","slug":"phosphatidylserine","display_name":"Phosphatidylserine","entity_type_key":"lipid"},"evidence_count":1,"mechanism_event":{"id":"a3ee856c-7180-5d29-aca8-ad70e46dc17d","stable_key":"649e861b-265a-5912-bc36-3a73e53ef892:l-serine-pss1-exchange-event","event_type":"observed_relationship","label":"Serine can replace a phospholipid headgroup to make a different membrane lipid.","description":"Purified human PSS1 reconstituted with phosphatidylcholine showed serine base-exchange activity producing phosphatidylserine.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"0b5548b5-3cd8-5f19-8eea-dfae2a671fb3","slug":"ptdss1","display_name":"Human phosphatidylserine synthase 1 / PTDSS1","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"0e2dd859-6135-556e-938f-d177f1e8c1ad","slug":"phosphatidylserine","display_name":"Phosphatidylserine","entity_type_key":"lipid"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"c882cd0b-9d83-5b07-bd1c-fe4d45657dcb","slug":"l-serine","display_name":"L-Serine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"2f77ef6d-3ecd-5a80-9ca3-3cbea403d9fc","slug":"phosphatidylcholine","display_name":"Phosphatidylcholine","entity_type_key":"lipid"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary full text","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human PSS1 proteoliposomes with POPC and radioactive serine assays.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"The bound endogenous lipid density could not conclusively distinguish PC from PE; no universal exclusion of PE is asserted.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Serine collection; species, compartment, exposure, co-substrates and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"l-serine","display_name":"L-Serine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"Serine can replace a phospholipid headgroup to make a different membrane lipid.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Structural basis for catalytic mechanism of human phosphatidylserine synthase 1. · 2025 · https://pubmed.ncbi.nlm.nih.gov/40044636/ · DOI 10.1038/s41421-025-00775-3","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"6f967b37-e2cc-51d5-a587-97cfa3ceb96e","evidence_kind":"source_excerpt","locator":"Lines 246-252","start_line":246,"end_line":252,"excerpt":"## l-serine-pss1-exchange\nSerine can replace a phospholipid headgroup to make a different membrane lipid.\nPurified human PSS1 reconstituted with phosphatidylcholine showed serine base-exchange activity producing phosphatidylserine.\nModel: Human PSS1 proteoliposomes with POPC and radioactive serine assays.\nLimitations: The bound endogenous lipid density could not conclusively distinguish PC from PE; no universal exclusion of PE is asserted.\nEvidence access: Primary full text\nStructural basis for catalytic mechanism of human phosphatidylserine synthase 1. · 2025 · https://pubmed.ncbi.nlm.nih.gov/40044636/ · DOI 10.1038/s41421-025-00775-3","model_system":"Human PSS1 proteoliposomes with POPC and radioactive serine assays.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access and experimental limitations specified.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"70bcf57a-36bb-563f-9073-2d616e5f155a","stable_key":"import-649e861b-265a-5912-bc36-3a73e53ef892","title":"L-Serine: synthesis, one-carbon metabolism, lipids and cross-nutrient mechanisms (2026-09-19)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text.","file_path":"","sha256":"22a750ce2b94f8607268c58322c48c4f0468f403b72a4008307538a6e5ff86d5","revision_id":"c1d6a7e1-9558-5bc6-9e3b-7080c26d3dbc","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}