chemistry

S-Nitrosoglutathione

S-Nitrosoglutathione is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand S-Nitrosoglutathione rather than just read about it. In short: S-Nitrosoglutathione (GSNO) is an endogenous S-nitrosothiol (SNO) that plays a critical role in nitric oxide (NO) signaling and is a source of bioavailable NO. NO coexists in cells with SNOs that serve as endogenous NO carriers and donors.

Key takeaways

S-Nitrosoglutathione belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect S-Nitrosoglutathione to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of S-Nitrosoglutathione from memory before moving on to harder problems.

Reference excerpt

S-Nitrosoglutathione (GSNO) is an endogenous S-nitrosothiol (SNO) that plays a critical role in nitric oxide (NO) signaling and is a source of bioavailable NO. NO coexists in cells with SNOs that serve as endogenous NO carriers and donors. SNOs spontaneously release NO at different rates and can be powerful terminators of free radical chain propagation reactions, by reacting directly with ROO• radicals, yielding nitro derivatives as end products. NO is generated intracellularly by the nitric oxide synthase (NOS) family of enzymes: nNOS, eNOS and iNOS while the in vivo source of many of the SNOs is unknown. In oxygenated buffers, however, formation of SNOs is due to oxidation of NO to dinitrogen trioxide (N2O3). Some evidence suggests that both exogenous NO and endogenously derived NO from nitric oxide synthases can react with glutathione to form GSNO.

GSNOR The enzyme GSNO reductase (GSNOR) reduces S-nitrosoglutathione (GSNO) to an unstable intermediate, S-hydroxylaminoglutathione, which then rearranges to form glutathione sulfonamide, or in the presence of GSH, forms glutathione disulfide and hydroxylamine.

Through this catabolic process, GSNOR regulates the cellular concentrations of GSNO and plays a central role in regulating the levels of endogenous S-nitrosothiols and controlling protein S-nitrosylation-based signaling.

The generation of GSNO can serve as a stable and mobile NO pool which can effectively transduce NO signaling. Unlike other low molecular weight messengers that bind to and activate target cellular receptors, NO signaling is mediated by a coordinating complex between NO and transition metals or target cellular proteins, often via S-nitrosylation of cysteine residues. Studies suggest that NO metabolism has a significant role in human cardiovascular and respiratory diseases as well as in immune tolerance during organ transplantation.

GSNO in health and disease GSNO and NO concentrations regulate respiratory function by modulating airway tone and pro- and anti-inflammatory responses in the respiratory tract. Because NO is a labile gas and endogenous levels are difficult to manipulate, it has been proposed that exogenous GSNO could be used to regulate circulating levels of NO and NO-derived species, and GSNO could have value in patients with pulmonary diseases such as cystic fibrosis. Consistent with this therapeutic goal, a recent study showed that acute treatment with aerosolized GSNO was well tolerated by cystic fibrosis patients. SNOs in the hepatic mitochondria appear to influence proper functioning of the liver. Mitochondrial SNO-proteins inhibit Complex I of the electron transport chain; modulate mitochondrial reactive oxygen species (ROS) production; influence calcium-dependent opening of the mitochondrial permeability transition pore; promote selective importation of mitochondrial proteins; and stimulate mitochondrial fission. Altered redox balance plays a crucial role in the pathogenesis of liver diseases including steatosis, steatohepatitis, and fibrosis. The ease of reversibility and the interplay of S-nitrosating and denitrosating enzymatic reactions support the hypothesis that SNOs regulate the mitochondrion through redox mechanisms. In a study evaluating the effects on ursodeoxycholic acid (UDCA) on bile flow and cirrhosis, NO was found in bile as SNOs, primarily GSNO. UDCA-stimulated biliary NO secretion was abolished by the inhibition of iNOS with L-NAME in isolated perfused livers and also in rat livers depleted of GSH with buthionine sulfoximine. Moreover, the biliary secretion of NO species was significantly diminished in UDCA-infused transport mutant [ATP–binding cassette C2/multidrug resistance–associated protein 2–deficient] rats, and this finding was consistent with the involvement of the glutathione carrier ABCC2/Mrp2 in the canalicular transport of GSNO. It was particularly noteworthy that in cultured normal rat cholangiocytes, GSNO activated protein kinase B, protected against apoptosis, and enhanced UDCA-induced ATP release to the medium. Finally, they demonstrated that retrograde GSNO infusion into the common bile duct increased bile flow and biliary bicarbonate secretion. The study concluded that UDCA-induced biliary secretion of GSNO contributed to stimulating ductal secretion of bile.

Neuromodulator GSNO, along with glutathione and oxidized glutathione (GSSG), have been found to bind to the glutamate recognition site of the NMDA and AMPA receptors (via their γ-glutamyl moieties), and may be endogenous neuromodulators. At millimolar concentrations, they may also modulate the redox state of the NMDA receptor complex.

References

for the synthesis of S-Nitrosoglutathione see Hart, T.W., 1985. Some observations concerning the S-nitroso and S-phenylsulphonyl derivatives of L-cysteine and glutathione. Tetrahedron Letters, 26(16), pp.2013-2016.

External links S-Nitrosoglutathione at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

Illustrations

Worked examples

Example 1 — a first encounter with S-Nitrosoglutathione

Start with the simplest possible case. Write down what S-Nitrosoglutathione claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to S-Nitrosoglutathione before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about S-Nitrosoglutathione ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of S-Nitrosoglutathione

In research: S-Nitrosoglutathione appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses S-Nitrosoglutathione in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: S-Nitrosoglutathione is common in secondary-school and first-year university syllabi. It links to neighbouring topics Excitatory amino acid receptor ligands, Neurotransmitters, Nitroso compounds, so understanding it makes those chapters shorter.
In everyday life: Look for S-Nitrosoglutathione outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study S-Nitrosoglutathione in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what S-Nitrosoglutathione means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain S-Nitrosoglutathione out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is S-Nitrosoglutathione in simple terms?

Why does S-Nitrosoglutathione matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study S-Nitrosoglutathione?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on S-Nitrosoglutathione.