{"id":"80a958b8-9e69-503f-b289-1516e8a0e92e","stable_key":"be889add-cec8-500b-be89-676431432a70:mn-enz-ovine-glul-metal-kinetics","predicate":"depends_on","statement":"Ovine brain GLUL assays showed optimal Mg:ATP at 2:1 and Mn:ATP at 1:1, with different reported pH optima of 7.5 and 5.0, respectively.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"4295becf-ad33-5588-8141-9cc731d3c18d","mechanism_event_label":"Magnesium and manganese supported GLUL under different assay conditions.","subject":{"id":"8f613a27-6378-5cce-98c4-21b4e13c1708","slug":"ovine-glul","display_name":"Ovine glutamine synthetase / GLUL","entity_type_key":"protein"},"object":{"id":"f6db8432-01e2-5341-9f70-73802ea56f27","slug":"glul-metal-dependent-activity","display_name":"Glutamine synthetase metal-dependent assay activity","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"4295becf-ad33-5588-8141-9cc731d3c18d","stable_key":"be889add-cec8-500b-be89-676431432a70:mn-enz-ovine-glul-metal-kinetics-event","event_type":"biochemical_relationship","label":"Magnesium and manganese supported GLUL under different assay conditions.","description":"Ovine brain GLUL assays showed optimal Mg:ATP at 2:1 and Mn:ATP at 1:1, with different reported pH optima of 7.5 and 5.0, respectively.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"8f613a27-6378-5cce-98c4-21b4e13c1708","slug":"ovine-glul","display_name":"Ovine glutamine synthetase / GLUL","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"f6db8432-01e2-5341-9f70-73802ea56f27","slug":"glul-metal-dependent-activity","display_name":"Glutamine synthetase metal-dependent assay activity","entity_type_key":"cellular_process"},"role":"object","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"bff427ab-35f9-59c2-bb24-fd5953bbaec2","slug":"magnesium-ion","display_name":"Mg2+","entity_type_key":"ion"},"role":"assay activator","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"a8082b11-c484-5792-bb81-48e8e699cbe4","slug":"manganese-ion","display_name":"Mn2+","entity_type_key":"ion"},"role":"assay activator","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"58b974f1-d389-5bf6-81cd-889c44442c42","slug":"atp","display_name":"ATP","entity_type_key":"small_molecule"},"role":"substrate","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"Mn and Mg can support activity in vitro, with distinct metal:ATP ratios and pH conditions.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Ovine brain glutamine synthetase steady-state kinetics and metal-binding measurements","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Mn(II) and Mg(II) titrations; binding and tissue metal measurements","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Different assay optima are not evidence that Mn is the preferred cofactor at physiological brain pH.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Manganese research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"manganese","display_name":"Manganese","entity_type_key":"nutrient_element"}},{"dimension":"organism","value_text":"Ovis aries","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Magnesium and manganese supported GLUL under different assay conditions.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[mn-enz-6129892] Glutamine synthetase from ovine brain is a manganese(II) enzyme. (1982). https://pubmed.ncbi.nlm.nih.gov/6129892/ DOI: 10.1021/bi00268a011","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Brain-derived purified enzyme","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"59802bd3-120b-57e2-af08-78641a8ad650","evidence_kind":"source_excerpt","locator":"Lines 620-631","start_line":620,"end_line":631,"excerpt":"### mn-enz-ovine-glul-metal-kinetics\nOvine brain GLUL assays showed optimal Mg:ATP at 2:1 and Mn:ATP at 1:1, with different reported pH optima of 7.5 and 5.0, respectively.\nCondition category: normal\nnutrient_topic: Manganese research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Magnesium and manganese supported GLUL under different assay conditions.\norganism: Ovis aries\ntissue_or_cell_type: Brain-derived purified enzyme\nexperimental_model: Ovine brain glutamine synthetase steady-state kinetics and metal-binding measurements\nlimitations: Different assay optima are not evidence that Mn is the preferred cofactor at physiological brain pH.\nexposure: Mn(II) and Mg(II) titrations; binding and tissue metal measurements\ncross_nutrient: Mn and Mg can support activity in vitro, with distinct metal:ATP ratios and pH conditions.\n[mn-enz-6129892] Glutamine synthetase from ovine brain is a manganese(II) enzyme. (1982). https://pubmed.ncbi.nlm.nih.gov/6129892/ DOI: 10.1021/bi00268a011","model_system":"Ovine brain glutamine synthetase steady-state kinetics and metal-binding measurements","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [mn-enz-6129892] Glutamine synthetase from ovine brain is a manganese(II) enzyme. (1982). https://pubmed.ncbi.nlm.nih.gov/6129892/ DOI: 10.1021/bi00268a011","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"03224387-8a73-5b4f-906d-9f0be6625b7f","stable_key":"import-be889add-cec8-500b-be89-676431432a70","title":"Manganese: enzyme cofactors, glycosylation, transport and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. 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