Iduronic acid

Iduronic acid
IUPAC name	L-idopyranuronic acid
Other names	L-Iduronic acid, D-ido-Hexuronic acid, IdoA
Identifiers
CAS number	3402-98-0
PubChem	18845
KEGG	C06472
MeSH	Iduronic+acid
ChEBI	28481
SMILES	O[C@H]1[C@H](O)[C@@H](O[C@@H](O)[C@@H]1O)C(=O)O
Properties
Molecular formula	C6H10O7
Molar mass	194.14 g mol−1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

L-Iduronic acid (IdoA) is the major uronic acid component of the glycosaminoglycans (GAGs) dermatan sulfate and heparin. It is also present in heparan sulfate although here in a minor amount relative to its carbon-5 epimer glucuronic acid.

IdoA is a hexapyranose sugar. Most hexapyranoses are stable in one of two chair conformations ¹C₄ or ⁴C₁. L-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 a O-sulfate group at carbon position 2 to form 2-O-sulfo-L-iduronic acid (IdoA2S).

In 2000, LK Hallak described the importance of this sugar in respiratory syncytial virus infection. Deramatn 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 can be used to track changes in the balance of this equilibrium.^[1]

IdoA(2S)1C4 conformation

IdoA(2S)2S0 conformation

References

1. ^ Ferro, D. R. Provasoli, A. (1990). "Conformer populations of L-iduronic acid residues in glycosaminoglycan sequences". Carbohydr. Res. 195: 157–167. doi:10.1016/0008-6215(90)84164-P. PMID 2331699.