{"id":"ec7ac5f5-019f-504c-bfb4-25148bfa2da0","stable_key":"649e861b-265a-5912-bc36-3a73e53ef892:l-serine-pstk-serine","predicate":"phosphorylates","statement":"Human PSTK phosphorylates serine attached to tRNA Sec as part of the specialized selenocysteine synthesis pathway.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"7a72ea78-0739-52cc-909c-297af2685a24","mechanism_event_label":"A serine molecule already loaded onto a tRNA is processed into a selenium-containing amino-acid precursor.","subject":{"id":"3f980f0c-89b2-5c6e-9d34-fc323ee2d2d8","slug":"pstk","display_name":"Human phosphoseryl-tRNA kinase / PSTK","entity_type_key":"protein"},"object":{"id":"7b6e13c8-a93e-593f-892e-e846847bd28a","slug":"seryl-trna-sec","display_name":"Seryl-tRNA Sec","entity_type_key":"rna"},"evidence_count":1,"mechanism_event":{"id":"7a72ea78-0739-52cc-909c-297af2685a24","stable_key":"649e861b-265a-5912-bc36-3a73e53ef892:l-serine-pstk-serine-event","event_type":"observed_relationship","label":"A serine molecule already loaded onto a tRNA is processed into a selenium-containing amino-acid precursor.","description":"Human PSTK phosphorylates serine attached to tRNA Sec as part of the specialized selenocysteine synthesis pathway.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"3f980f0c-89b2-5c6e-9d34-fc323ee2d2d8","slug":"pstk","display_name":"Human phosphoseryl-tRNA kinase / PSTK","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"7b6e13c8-a93e-593f-892e-e846847bd28a","slug":"seryl-trna-sec","display_name":"Seryl-tRNA Sec","entity_type_key":"rna"},"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":"5b2eb213-ab47-5a57-871a-e00a5ef02990","slug":"phosphoseryl-trna-sec","display_name":"O-phosphoseryl-tRNA Sec","entity_type_key":"rna"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified human PSTK with tRNA substrates; comparison with KTI12.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"This is tRNA-bound serine chemistry, not direct conversion of free serine into free selenocysteine.","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":"A serine molecule already loaded onto a tRNA is processed into a selenium-containing amino-acid precursor.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Same but different - Molecular comparison of human KTI12 and PSTK. · 2021 · https://pubmed.ncbi.nlm.nih.gov/33417976/ · DOI 10.1016/j.bbamcr.2020.118945","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"69cb747b-da44-50a8-827d-51b78cacec11","evidence_kind":"source_excerpt","locator":"Lines 382-388","start_line":382,"end_line":388,"excerpt":"## l-serine-pstk-serine\nA serine molecule already loaded onto a tRNA is processed into a selenium-containing amino-acid precursor.\nHuman PSTK phosphorylates serine attached to tRNA Sec as part of the specialized selenocysteine synthesis pathway.\nModel: Purified human PSTK with tRNA substrates; comparison with KTI12.\nLimitations: This is tRNA-bound serine chemistry, not direct conversion of free serine into free selenocysteine.\nEvidence access: Primary abstract\nSame but different - Molecular comparison of human KTI12 and PSTK. · 2021 · https://pubmed.ncbi.nlm.nih.gov/33417976/ · DOI 10.1016/j.bbamcr.2020.118945","model_system":"Purified human PSTK with tRNA substrates; comparison with KTI12.","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}