{"id":"d72834c2-d868-5e92-bc73-2a9ec7e7b01d","stable_key":"252872b9-233f-5692-b72b-c8930ba0cfb7:sil-allosteric-sites-gate-phosphorylation","predicate":"modulates","statement":"Mutations affecting cyclic GMP binding to either one or both allosteric sites of phosphodiesterase type 5 do not influence cyclic GMP hydrolysis at the catalytic site under the conditions used, but the mutants defective in binding at either site require much higher cyclic GMP concentrations for allosteric stimulation of phosphorylation, while a mutant with higher binding affinity is phosphorylated at lower cyclic GMP concentrations, so binding to the allosteric sites does not directly affect catalysis but regulates phosphorylation of the enzyme.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"b286321a-f5ee-55dc-8711-631980c553d9","mechanism_event_label":"The second pair of binding sites does not change how fast the enzyme works; 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zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"f59d258bd35b229b3455ab2d15e1d21fbe5a475a1b936ecd423eb49c9a9aea29\", \"start_char\": 0, \"end_char\": 1541, \"text_sha256\": \"f59d258bd35b229b3455ab2d15e1d21fbe5a475a1b936ecd423eb49c9a9aea29\"}","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Site-directed mutagenesis of the two tandem allosteric cyclic GMP binding sites of phosphodiesterase type 5","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"D289A, D478A and D289A/D478A binding-site mutants, with phosphorylation by the catalytic subunit of cyclic AMP-dependent protein kinase","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Separates what the allosteric sites do from what the catalytic site does, using mutants that lose binding at one site, the other, or both.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Sildenafil research collection; 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