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Chemiluminescence-based Assays for Detection of Nitric Oxide and its Derivatives from Autoxidation and Nitrosated Compounds
Published on: February 16, 2022
Fast ferrous heme-NO oxidation in nitric oxide synthases
Jesús Tejero1, Jérôme Santolini, Dennis J Stuehr
1Department of Pathobiology, The Cleveland Clinic Foundation, Lerner Research Institute, 9500 Euclid Ave., Cleveland, OH 44195, USA.
The FEBS Journal
|August 20, 2009
Summary
Nitric oxide synthase (NOS) enzymes utilize a heme-NO complex. Oxygen directly oxidizes this complex, a novel mechanism distinguishing heme-thiolate enzymes.
Area of Science:
- Biochemistry
- Enzymology
- Chemical Kinetics
Background:
- Nitric oxide synthase (NOS) enzymes catalyze the production of nitric oxide (NO).
- The catalytic cycle involves the binding and release of NO by the heme prosthetic group.
- Oxidation of the ferrous heme-NO complex by molecular oxygen (O2) is crucial for enzyme turnover, but its mechanism remains poorly understood.
Purpose of the Study:
- To elucidate the mechanism of O2 oxidation of the ferrous heme-NO complex in NOS enzymes.
- To investigate whether heme-NO dissociation precedes O2 reaction.
Main Methods:
- Stopped-flow spectroscopy was employed to monitor rapid reaction kinetics.
- The reaction of O2 with purified inducible and neuronal NOS enzymes containing ferrous heme-NO complexes was studied.
Main Results:
- The reaction of O2 with the ferrous heme-NO complex was found to be rapid.
- Evidence indicated that the reaction proceeds via direct oxidation of the ferrous heme-NO complex.
- Heme-NO dissociation was not observed to be a prerequisite for O2 reaction.
Conclusions:
- The oxidation of the ferrous heme-NO complex in NOS enzymes occurs through a direct reaction with O2.
- This direct oxidation mechanism is a novel finding for heme-thiolate enzymes.
- This mechanism may differentiate NOS enzymes from other heme proteins.
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