-Iduronic acid (

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

abbr.: IdoA) is the major uronic acid component of the

glycosaminoglycans Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case ...

(GAGs)

dermatan sulfate Dermatan sulfate is a glycosaminoglycan (formerly called a mucopolysaccharide) found mostly in skin, but also in blood vessels, heart valves, tendons, and lungs. It is also referred to as chondroitin sulfate B, although it is no longer classifie ...

, and

heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Since heparins depend on the activity of antithrombin, they are considered anticoagulants. Specifically it is also used in the treatm ...

. It is also present in

heparan sulfate Heparan sulfate (HS) is a linear polysaccharide found in all animal tissues. It occurs as a proteoglycan (HSPG, i.e. Heparan Sulfate ProteoGlycan) in which two or three HS chains are attached in close proximity to cell surface or extracellular ma ...

, although here in a minor amount relative to its carbon-5

epimer In stereochemistry, an epimer is one of a pair of diastereomers. The two epimers have opposite configuration at only one stereogenic center out of at least two. All other stereogenic centers in the molecules are the same in each. Epimerization is ...

glucuronic acid Glucuronic acid (from Greek γλεῦκος "''wine, must''" and οὖρον "''urine''") is a uronic acid that was first isolated from urine (hence the name). It is found in many gums such as gum arabic (c. 18%), xanthan, and kombucha tea and ...

. IdoA is a hexapyranose sugar. Most hexapyranoses are stable in one of two chair conformations ¹C₄ or ⁴C₁. -iduronate is different and adopts more than one solution conformation, with an equilibrium existing between three low-energy conformers. These are the ¹C₄ and ⁴C₁ chair forms and an additional ²S₀ skew-boat conformation. IdoA may be modified by the addition of an ''O''-sulfate group at carbon position 2 to form 2-''O''-sulfo--iduronic acid (IdoA2S). In 2000, LK Hallak described the importance of this sugar in respiratory syncytial virus (RSV) infection. Dermatan sulfate and heparan sulfate were the only GAGs containing IdoA, and they were the only ones that inhibited RSV infection in cell culture. When internally positioned within an oligosaccharide, the ¹C₄ and ²S₀ conformations (shown below for IdoA2S) predominate. Proton

NMR spectroscopy Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fiel ...

can be used to track changes in the balance of this equilibrium.{{cite journal , author=Ferro, D. R. Provasoli, A. , title=Conformer populations of L-iduronic acid residues in glycosaminoglycan sequences , journal=Carbohydr. Res. , year=1990 , volume=195 , pages=157–167 , pmid=2331699 , doi=10.1016/0008-6215(90)84164-P , issue=2 File:IDU_1C4.jpeg, IdoA(2S)¹C₄ conformation File:IDU_2S0.jpeg, IdoA(2S)²S₀ conformation

References

Uronic acids