Nitric oxide synthase 1 (neuronal), also known as NOS1, is an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that in humans is encoded by the NOS1 gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

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Function

Nitric oxide

Nitric oxide

Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...

 (NO) is a messenger molecule with diverse functions throughout the body. In the brain and peripheral nervous system, NO displays many properties of a neurotransmitter

Neurotransmitter

Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...

; it is implicated in neurotoxicity

Neurotoxicity

Neurotoxicity occurs when the exposure to natural or artificial toxic substances, which are called neurotoxins, alters the normal activity of the nervous system in such a way as to cause damage to nervous tissue. This can eventually disrupt or even kill neurons, key cells that transmit and process...

 associated with stroke

Stroke

A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...

 and neurodegenerative diseases, neural regulation of smooth muscle, including peristalsis

Peristalsis

Peristalsis is a radially symmetrical contraction and relaxation of muscles which propagates in a wave down the muscular tube, in an anterograde fashion. In humans, peristalsis is found in the contraction of smooth muscles to propel contents through the digestive tract. Earthworms use a similar...

, and penile erection. NO is also responsible for endothelium-derived relaxing factor

Endothelium-derived relaxing factor

Endothelium-derived relaxing factor is produced and released by the endothelium to promote smooth muscle relaxation. The best-characterized is nitric oxide . Some sources equate EDRF and nitric oxide....

 activity regulating blood pressure. In macrophage

Macrophage

Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...

s, NO mediates tumoricidal and bactericidal actions, as indicated by the fact that inhibitors of NO synthase (NOS) block these effects. Neuronal NOS and macrophage NOS

Nitric oxide synthase 2A

Nitric oxide synthase, inducible is an enzyme that in humans is encoded by the NOS2 gene.Nitric oxide is a reactive free radical which acts as a biologic mediator in several processes, including neurotransmission and antimicrobial and antitumoral activities...

 are distinct isoforms. Both the neuronal and the macrophage forms are unusual among oxidative enzymes in requiring several electron donors: FAD

FAD

In biochemistry, flavin adenine dinucleotide is a redox cofactor involved in several important reactions in metabolism. FAD can exist in two different redox states, which it converts between by accepting or donating electrons. The molecule consists of a riboflavin moiety bound to the phosphate...

, flavin mononucleotide

Flavin mononucleotide

Flavin mononucleotide , or riboflavin-5′-phosphate, is a biomolecule produced from riboflavin by the enzyme riboflavin kinase and functions as prosthetic group of various oxidoreductases including NADH dehydrogenase as well as cofactor in biological blue-light photo receptors...

 (FMN), NADPH, and tetrahydrobiopterin

Tetrahydrobiopterin

Tetrahydrobiopterin or sapropterin is a naturally occurring essential cofactor of the three aromatic amino acid hydroxylase enzymes, used in the degradation of amino acid phenylalanine and in the biosynthesis of the neurotransmitters serotonin , melatonin, dopamine, norepinephrine ,...

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Clinical significance

It has been implicated in asthma

Asthma

Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

, schizophrenia

Schizophrenia

Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...

 and restless leg syndrome. It has also been investigated with respect to bipolar disorder

Bipolar disorder

Bipolar disorder or bipolar affective disorder, historically known as manic–depressive disorder, is a psychiatric diagnosis that describes a category of mood disorders defined by the presence of one or more episodes of abnormally elevated energy levels, cognition, and mood with or without one or...

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Interactions

NOS1 has been shown to interact

Protein-protein interaction

Protein–protein interactions occur when two or more proteins bind together, often to carry out their biological function. Many of the most important molecular processes in the cell such as DNA replication are carried out by large molecular machines that are built from a large number of protein...

 with DLG4

DLG4

PSD-95 also known as SAP-90 is a protein that in humans is encoded by the DLG4 gene....

 and NOS1AP

NOS1AP

Nitric oxide synthase 1 adaptor protein also known as carboxyl-terminal PDZ ligand of neuronal nitric oxide synthase protein is a protein that in humans is encoded by the NOS1AP gene....

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Further reading