{"id":"86a4e878-8374-5f86-9b4e-f9fcf1fb2361","stable_key":"56f1d914-e7da-595a-af69-c217b2b47407:l-phenylalanine-tyrosine-next-step","predicate":"hydroxylates","statement":"Human tyrosine hydroxylase catalyzes BH4-dependent tyrosine hydroxylation to L-DOPA, a downstream step in dopamine biosynthesis.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"ecb4d705-fb62-5740-996b-50cc0651a411","mechanism_event_label":"Producing tyrosine is only the first part of the route toward dopamine.","subject":{"id":"e4e0f24b-1e70-573d-b719-039a90191b90","slug":"human-tyrosine-hydroxylase","display_name":"Human tyrosine hydroxylase","entity_type_key":"protein"},"object":{"id":"d2e54a66-7f3c-5bcc-adbe-9f66ad4264f4","slug":"l-dopa","display_name":"L-3,4-Dihydroxyphenylalanine","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"ecb4d705-fb62-5740-996b-50cc0651a411","stable_key":"56f1d914-e7da-595a-af69-c217b2b47407:l-phenylalanine-tyrosine-next-step-event","event_type":"observed_relationship","label":"Producing tyrosine is only the first part of the route toward dopamine.","description":"Human tyrosine hydroxylase catalyzes BH4-dependent tyrosine hydroxylation to L-DOPA, a downstream step in dopamine biosynthesis.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"e4e0f24b-1e70-573d-b719-039a90191b90","slug":"human-tyrosine-hydroxylase","display_name":"Human tyrosine hydroxylase","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"d2e54a66-7f3c-5bcc-adbe-9f66ad4264f4","slug":"l-dopa","display_name":"L-3,4-Dihydroxyphenylalanine","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"190407ad-0219-54b5-b05f-7c75f3895ca6","slug":"l-phenylalanine","display_name":"L-Phenylalanine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"bcfef85f-831d-5439-ba51-1aef4b090441","slug":"l-tyrosine","display_name":"L-Tyrosine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"1c231b90-c106-507a-8766-870ecb40e368","slug":"tetrahydrobiopterin","display_name":"Tetrahydrobiopterin / BH4","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 TH variant study; established enzyme reaction described in the abstract.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"This is a downstream connection, not evidence that oral phenylalanine predictably raises brain dopamine.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"l-phenylalanine","display_name":"L-Phenylalanine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"Producing tyrosine is only the first part of the route toward dopamine.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Tyrosine hydroxylase variants influence protein expression, cellular localization, stability, enzymatic activity and the physical interaction between tyrosine hydroxylase and GTP cyclohydrolase 1. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38084654/ · DOI 10.1002/jimd.12690","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"89ea7568-a6ee-5060-93ee-1608ab70bd61","evidence_kind":"source_excerpt","locator":"Lines 118-124","start_line":118,"end_line":124,"excerpt":"## l-phenylalanine-tyrosine-next-step\nProducing tyrosine is only the first part of the route toward dopamine.\nHuman tyrosine hydroxylase catalyzes BH4-dependent tyrosine hydroxylation to L-DOPA, a downstream step in dopamine biosynthesis.\nModel: Human TH variant study; established enzyme reaction described in the abstract.\nLimitations: This is a downstream connection, not evidence that oral phenylalanine predictably raises brain dopamine.\nEvidence access: Primary abstract\nTyrosine hydroxylase variants influence protein expression, cellular localization, stability, enzymatic activity and the physical interaction between tyrosine hydroxylase and GTP cyclohydrolase 1. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38084654/ · DOI 10.1002/jimd.12690","model_system":"Human TH variant study; established enzyme reaction described in the abstract.","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":"54de7c56-1e60-5d7b-8ef9-852c58ae92ba","stable_key":"import-56f1d914-e7da-595a-af69-c217b2b47407","title":"L-Phenylalanine: transport, protein synthesis, cofactor recycling 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. 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