Fast ferrous heme-NO oxidation in nitric oxide synthases
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Updated: Jun 20, 2026

Chemiluminescence-based Assays for Detection of Nitric Oxide and its Derivatives from Autoxidation and Nitrosated Compounds
Published on: February 16, 2022
Jesús Tejero1, Jérôme Santolini, Dennis J Stuehr
1Department of Pathobiology, The Cleveland Clinic Foundation, Lerner Research Institute, 9500 Euclid Ave., Cleveland, OH 44195, USA.
Abstract:
During catalysis, the heme in nitric oxide synthase (NOS) binds NO before releasing it to the environment. Oxidation of the NOS ferrous heme-NO complex by O2 is key for catalytic cycling, but the mechanism is unclear. We utilized stopped-flow methods to study the reaction of O2 with ferrous heme-NO complexes of inducible and neuronal NOS enzymes. We found that the reaction does not involve heme-NO dissociation, but instead proceeds by a rapid direct reaction of O2 with the ferrous heme-NO complex. This behavior is novel and may distinguish heme-thiolate enzymes, such as NOS, from related heme proteins.
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