chemistry

Indoxyl sulfate

Indoxyl sulfate 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 Indoxyl sulfate rather than just read about it. In short: Indoxyl sulfate, also known as 3-indoxylsulfate and 3-indoxylsulfuric acid, is a metabolite of dietary L-tryptophan that acts as a cardiotoxin and uremic toxin. High concentrations of indoxyl sulfate in blood plasma are known to be associated with the development and progression of chronic kidney disease and vascular disease in humans.

Key takeaways

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

Reference excerpt

Indoxyl sulfate, also known as 3-indoxylsulfate and 3-indoxylsulfuric acid, is a metabolite of dietary L-tryptophan that acts as a cardiotoxin and uremic toxin. High concentrations of indoxyl sulfate in blood plasma are known to be associated with the development and progression of chronic kidney disease and vascular disease in humans. As a uremic toxin, it stimulates glomerular sclerosis and renal interstitial fibrosis.

Biosynthesis Indoxyl sulfate is a metabolite of dietary L-tryptophan that is synthesized through the following metabolic pathway:

L-tryptophan → indole → indoxyl → indoxyl sulfate Indole is produced from L-tryptophan in the human intestine via tryptophanase-expressing gastrointestinal bacteria. Indoxyl is produced from indole via enzyme-mediated hydroxylation in the liver; in vitro experiments with rat and human liver microsomes suggest that the CYP450 enzyme CYP2E1 hydroxylates indole into indoxyl. Subsequently, indoxyl is converted into indoxyl sulfate by sulfotransferase enzymes in the liver; based upon in vitro experiments with recombinant human sulfotransferases, SULT1A1 appears to be the primary sulfotransferase enzyme involved in the conversion of indoxyl into indoxyl sulfate.

Clinical significance Occasionally in urinary tract infections, bacteria produce indoxyl phosphatase which splits indoxyl sulfate forming indigo and indirubin creating dramatic purple urine. Indoxyl sulfate is also a product of indole metabolism, which is produced from tryptophan by intestinal flora, such as Escherichia coli. The amount of tryptophan in one's diet determines how much indoxyl sulfate may be created in the intestines. There is also high individual variability among a person's ability to convert a dose of tryptophan into indoxyl sulfate, as measured in an oral tryptophan challenge test. Indoxyl sulfate is considered a uremic toxin. It is not as effectively removed by kidney dialysis as by the kidney itself, leading to an accumulation in those relying on dialysis. Despite cell culture, animal, and association data suggesting that it may be toxic to various organs and play a role in kidney disease progression, no effects on CKD progression were seen in the largest study that attempts to lower its blood levels (AST-120) as of 2016. Some association studies additionally suggested that indoxyl sulfate may have a role in the elevated rates of cardiovascular disease in CKD patients.

Veterinary medicine In cats, plasma indoxyl sulfate level correlates with the CKD stage. It also predicts the extent of future progression and possibly disease onset. In dogs, plasma indoxyl sulfate level predicts future CKD progression.

References

Illustrations

Worked examples

Example 1 — a first encounter with Indoxyl sulfate

Start with the simplest possible case. Write down what Indoxyl sulfate 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 Indoxyl sulfate 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 Indoxyl sulfate 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 Indoxyl sulfate

In research: Indoxyl sulfate 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 Indoxyl sulfate 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: Indoxyl sulfate is common in secondary-school and first-year university syllabi. It links to neighbouring topics Amino acid derivatives, Indoles, Organosulfates, so understanding it makes those chapters shorter.
In everyday life: Look for Indoxyl sulfate 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 Indoxyl sulfate in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Indoxyl sulfate 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 Indoxyl sulfate out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Indoxyl sulfate in simple terms?

Why does Indoxyl sulfate 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 Indoxyl sulfate?

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 Indoxyl sulfate.