{"id":"a89195da-00f9-59f5-965d-400dcb0faece","stable_key":"fd37d270-3395-56d6-9f1c-ddda56e606f6:arg-sms","predicate":"converted_to","statement":"Human spermine-synthase substrate/product structures and mutagenesis support aminopropyl transfer to spermidine.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"b4db8566-07a7-5bed-9182-c587b9060aca","mechanism_event_label":"The polyamine pathway extends beyond spermidine.","subject":{"id":"7014993c-468f-5c6b-ab04-80c87f9dfd9f","slug":"spermidine","display_name":"Spermidine","entity_type_key":"small_molecule"},"object":{"id":"ded80d0b-9076-5034-9e87-cd38f7dafae5","slug":"spermine","display_name":"Spermine","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"b4db8566-07a7-5bed-9182-c587b9060aca","stable_key":"fd37d270-3395-56d6-9f1c-ddda56e606f6:arg-sms-event","event_type":"observed_relationship","label":"The polyamine pathway extends beyond spermidine.","description":"Human spermine-synthase substrate/product structures and mutagenesis support aminopropyl transfer to spermidine.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"7014993c-468f-5c6b-ab04-80c87f9dfd9f","slug":"spermidine","display_name":"Spermidine","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"ded80d0b-9076-5034-9e87-cd38f7dafae5","slug":"spermine","display_name":"Spermine","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"0e161cf1-bc45-58f9-9177-05bba899c0bf","slug":"sms","display_name":"Human spermine synthase / SMS","entity_type_key":"protein"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"ae5a8bbb-59e5-503a-94c9-51b512d7c7b3","slug":"decarboxylated-sam","display_name":"Decarboxylated S-adenosylmethionine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"525860da-a986-5d19-97f0-a257a454b649","slug":"5-methylthioadenosine","display_name":"5′-Methylthioadenosine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human SMS structures and catalytic assays.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"A pathway connection does not mean arginine is always rate limiting.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Arginine collection; tissue, species, dose and formulation distinctions retained.","comparator":null,"unit":null,"notes":"","entity":{"slug":"arginine","display_name":"L-Arginine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"The polyamine pathway extends beyond spermidine.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Crystal structure of human spermine synthase: implications of substrate binding and catalytic mechanism. · 2008 · https://pubmed.ncbi.nlm.nih.gov/18367445/ · DOI 10.1074/jbc.m710323200","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"48c13849-9c76-5415-ae80-7a8db11e8972","evidence_kind":"source_excerpt","locator":"Lines 158-164","start_line":158,"end_line":164,"excerpt":"## arg-sms\nThe polyamine pathway extends beyond spermidine.\nHuman spermine-synthase substrate/product structures and mutagenesis support aminopropyl transfer to spermidine.\nModel: Human SMS structures and catalytic assays.\nLimitations: A pathway connection does not mean arginine is always rate limiting.\nEvidence access: Primary abstract\nCrystal structure of human spermine synthase: implications of substrate binding and catalytic mechanism. · 2008 · https://pubmed.ncbi.nlm.nih.gov/18367445/ · DOI 10.1074/jbc.m710323200","model_system":"Human SMS structures and catalytic assays.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; primary evidence access stated per claim.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"bb9a67ea-904f-5b8a-93a4-459081212bdd","stable_key":"import-fd37d270-3395-56d6-9f1c-ddda56e606f6","title":"L-Arginine: transport, metabolic branches, nutrient interactions, availability and discovery questions (2026-09-18)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary-abstract references and experimental limitations individually identified. 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