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Oxygen metabolism by neuronal nitric-oxide synthase.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 2007 Mar 16; Vol. 282 (11), pp. 7921-9. Date of Electronic Publication: 2007 Jan 17. - Publication Year :
- 2007
-
Abstract
- Nitric-oxide synthases (NOS) catalyze nitric oxide (NO) formation from the amino acid L-arginine. NOS is known to catalyze more than one reaction: the NO-producing reaction is considered to be the coupled reaction, and the uncoupled reactions are those that produce reactive (reduced) oxygen species (ROS), such as superoxide anion (O-2.) and/or hydrogen peroxide (H2O2). As an oxygenase, NOS has been known for more than two decades, yet there is no complete description of oxygen stoichiometry. The present paper is focused on oxygen stoichiometry and the effects of cofactor binding on the neuronal isoform (nNOS) on oxygen uptake and product formation. Products of the uncoupled reactions are analyzed using diacetyldeuteroheme-substituted horseradish peroxidase as a trapping agent for both O-2. and H2O2. The addition of calmodulin not only stimulated the oxygen uptake rate but also changed the product of the uncoupled reaction, supporting the possibility of two different sites for electron leakage to molecular oxygen. Quantitative analysis of the uncoupled (substrate-free) reaction revealed a stoichiometry close to the theoretical value, and adding L-arginine not only initiates the coupled reaction, but also inhibits oxygen uptake. The presence of tetrahydrobiopterin affects oxygen metabolism by lowering the apparent Km value of nNOS for oxygen in the uncoupled reaction.
- Subjects :
- Animals
Anions
Arginine chemistry
Calmodulin metabolism
Catalysis
Escherichia coli metabolism
Hydrogen Peroxide pharmacology
Kinetics
Models, Chemical
Oxygen Consumption
Reactive Oxygen Species
Substrate Specificity
Superoxides chemistry
Time Factors
Nitric Oxide Synthase Type I metabolism
Oxygen metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 282
- Issue :
- 11
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 17229730
- Full Text :
- https://doi.org/10.1074/jbc.M609814200