Related Experiment Video
Updated: Jul 17, 2026
08:32
Application of Genetically Encoded Fluorescent Nitric Oxide (NO•) Probes, the geNOps, for Real-time Imaging of NO• Signals in Single Cells
Published on: March 16, 2017
Oxygen metabolism by neuronal nitric-oxide synthase
Ying Tong Gao1, Satya Prakash Panda, Linda J Roman
1Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA.
The Journal of Biological Chemistry
|January 19, 2007
Summary
Nitric-oxide synthases (NOS) catalyze nitric oxide (NO) and reactive oxygen species (ROS). This study quantifies oxygen stoichiometry in neuronal NOS (nNOS), revealing cofactor binding impacts NO production and ROS formation.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Nitric-oxide synthases (NOS) are enzymes crucial for nitric oxide (NO) synthesis from L-arginine.
- NOS can undergo coupled (NO production) and uncoupled reactions (reactive oxygen species - ROS production).
- Despite decades of study, the precise oxygen stoichiometry of NOS remains incompletely understood.
Purpose of the Study:
- To investigate the oxygen stoichiometry of the neuronal isoform of nitric-oxide synthase (nNOS).
- To examine the influence of cofactor binding, specifically calmodulin and tetrahydrobiopterin, on nNOS oxygen metabolism.
- To analyze the products of both coupled and uncoupled reactions catalyzed by nNOS.
Main Methods:
- Utilized diacetyldeuteroheme-substituted horseradish peroxidase as a trapping agent for superoxide anion (O-2.) and hydrogen peroxide (H2O2).
- Quantitatively analyzed oxygen uptake and product formation under varying conditions, including substrate-free and substrate-bound states.
- Investigated the effects of calmodulin and tetrahydrobiopterin on nNOS activity and oxygen consumption.
Main Results:
- Calmodulin addition stimulated oxygen uptake and altered uncoupled reaction products, suggesting distinct electron leakage sites.
- Quantitative analysis of the uncoupled reaction showed stoichiometry near theoretical values.
- L-arginine addition initiated the coupled reaction and inhibited oxygen uptake, while tetrahydrobiopterin lowered the apparent Km for oxygen in the uncoupled reaction.
Conclusions:
- nNOS exhibits complex oxygen stoichiometry influenced by cofactor binding.
- Calmodulin and tetrahydrobiopterin play significant roles in modulating nNOS activity and the balance between NO and ROS production.
- Understanding nNOS oxygen metabolism is critical for elucidating its physiological and pathological roles.
Related Concept Videos
01:28Nitric Oxide Signaling Pathway
Nitric oxide (NO), an inorganic gas, acts as a potent second messenger in most animal and plant tissues. NO diffuses out of the cells that produce it and enters the neighboring cells to generate a downstream response. NO synthase (NOS) catalyzes NO production by the deamination of the amino acid arginine. There are three isoforms of NOS. Endothelial cells have endothelial NOS (eNOS), nerve and muscle cells have neuronal NOS (nNOS), and macrophages produce inducible NOS (iNOS) upon exposure to...
01:20Overview of Nitrogen Metabolism
Nitrogen is a very important element for life because it is a major constituent of proteins and nucleic acids. It is a macronutrient, and in nature, it is recycled from organic compounds and stored in the form of ammonia, ammonium ions, nitrate, nitrite, or nitrogen gas by many metabolic processes. Many of these metabolic processes are carried out only by prokaryotes.
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this nitrogen...
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this nitrogen...
01:22Physiology of Respiration II: Neurogenic Control of Respiration
The neurogenic control of respiration coordinates various neural networks and pathways to regulate breathing rate and depth, meeting the body's oxygen and carbon dioxide exchange requirements. This system adapts to physiological and environmental conditions, ensuring optimal breathing patterns.
Central Control
The brainstem is the primary site of central control, hosting respiratory centers:
Central Control
The brainstem is the primary site of central control, hosting respiratory centers:
01:27Oxygen Transport in the Blood
Hemoglobin (Hb) is a crucial molecule in the human body, consisting of four polypeptide chains, each bound to an iron-containing heme group. This unique structure enables hemoglobin to bind to oxygen, with each molecule capable of combining with four molecules of oxygen, leading to rapid and reversible oxygen loading. When fully loaded with oxygen, it is called oxyhemoglobin, while hemoglobin that has released oxygen is called reduced hemoglobin or deoxyhemoglobin. As hemoglobin binds oxygen,...