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.[1][2][3] 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.[1][2][3] As a uremic toxin, it stimulates glomerular sclerosis and renal interstitial fibrosis.[1][2]
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Preferred IUPAC name
1H-Indol-3-yl hydrogen sulfate | |
Other names
3-Indoxylsulfate; 3-Indoxylsulfuric acid; Indol-3-yl sulfate
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Identifiers | |
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3D model (JSmol)
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ChEBI |
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ChEMBL |
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ChemSpider |
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DrugBank |
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PubChem CID
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UNII |
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CompTox Dashboard (EPA)
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Properties | |
C8H7NO4S | |
Molar mass | 213.21 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
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Indoxyl sulfate is a metabolite of dietary L-tryptophan that is synthesized through the following metabolic pathway:[3][4][5]
Indole is produced from L-tryptophan in the human intestine via tryptophanase-expressing gastrointestinal bacteria.[3] Indoxyl is produced from indole via enzyme-mediated hydroxylation in the liver;[3][4] in vitro experiments with rat and human liver microsomes suggest that the CYP450 enzyme CYP2E1 hydroxylates indole into indoxyl.[4] Subsequently, indoxyl is converted into indoxyl sulfate by sulfotransferase enzymes in the liver;[4][5] 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.[5]
Tryptophan metabolism by human gastrointestinal microbiota ( )
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Occasionally in urinary tract infections, bacteria produce indoxyl phosphatase which splits indoxyl sulfate forming indigo and indirubin creating dramatic purple urine.[9] Indoxyl sulfate is also a product of indole metabolism, which is produced from tryptophan by intestinal flora, such as Escherichia coli.[10]
Lactobacillus spp. convert tryptophan to indole-3-aldehyde (I3A) through unidentified enzymes [125]. Clostridium sporogenes convert tryptophan to IPA [6], likely via a tryptophan deaminase. ... IPA also potently scavenges hydroxyl radicals
Production of IPA was shown to be completely dependent on the presence of gut microflora and could be established by colonization with the bacterium Clostridium sporogenes.
[Indole-3-propionic acid (IPA)] has previously been identified in the plasma and cerebrospinal fluid of humans, but its functions are not known. ... In kinetic competition experiments using free radical-trapping agents, the capacity of IPA to scavenge hydroxyl radicals exceeded that of melatonin, an indoleamine considered to be the most potent naturally occurring scavenger of free radicals. In contrast with other antioxidants, IPA was not converted to reactive intermediates with pro-oxidant activity.