What is the Difference Between Glucuronic Acid and Iduronic Acid

The main difference between glucuronic acid and iduronic acid is that glucuronic acid has a carboxyl group located on the first carbon atom (C1), whereas iduronic acid has a carboxyl group located on the second carbon atom (C2).

Uronic acids are sugar acids derived from the oxidation of carbohydrates. Glucuronic acid and iduronic acid are two different types of uronic acids. Both of these uronic acids are important components of glycosaminoglycans, which are long chains of complex sugars that help in a variety of biological processes, such as the lubrication of joints, maintenance of skin elasticity, regulation of cell growth, and differentiation.

Key Areas Covered

1. What is Glucuronic Acid 
     – Definition, Structure, Application
2. What is Iduronic Acid
     – Definition, Structure, Application
3. Difference Between Glucuronic Acid and Iduronic Acid
     – Comparison of Key Differences

Key Terms

Glucuronic Acid, Iduronic Acid

What is Glucuronic Acid

Glucuronic acid is a sugar acid that is derived from glucose through oxidation and has the molecular formula C₆H₁₀O₇. It has a carboxyl group located on the first carbon atom(C1). Moreover, glucuronic acids are naturally present in many organisms, such as plants and animals, including humans. It is an important component of glycosaminoglycans.

Furthermore, there are many functions of glucuronic acid. One main function of glucuronic acid is to detoxify foreign substances in the liver when certain foreign substances, like drugs and toxins, enter the body. They get metabolized by the liver into more water-soluble compounds that can be excreted in the urine or bile. Glucuronic acid is conjugated into these compounds by the enzyme UDP-glucuronosyltransferase, which makes them more water-soluble and easier to excrete.

Apart from its role in detoxification,  it also helps in synthesizing hyaluronic acid, a component of connective tissue such as skin and cartilage. Glucuronic acid also helps in the synthesis of chondroitin sulfate, which is another important component of cartilage.

What is Iduronic Acid

Iduronic acid is a major uronic acid component of glycosaminoglycans. It has a molecular formula of C₆H₁₀O₇  and is a hexopyranose sugar (a six-carbon sugar). Iduronic acid has a carboxyl group located on the second carbon atom(C2). Having a carboxyl group on C2 makes iduronic acid more acidic than glucuronic acid. This positioning also affects the way in which iduronic acid interacts with other molecules.

Iduronic acid is synthesized in the Golgi apparatus of the cells. Here, it is added to the growing chains of GAG molecules. A series of enzymatic reactions convert glucuronic acid into iduronic acids.

The presence of iduronic acid in GAG molecules affects biological activity and function. The degree of iduronic acid substitution in heparin can affect its anticoagulant properties. Heparin with more iduronic acid substitution is better at preventing blood clotting than heparin with less iduronic acid substitution.

Applications of Iduronic Acid

There are many important functions of iduronic acid. One function of iduronic acid is its role in the anticoagulant activity of heparin. Heparin is a naturally occurring GAG that is made in the mast cells and released into the bloodstream. The residues of iduronic acid in heparin are important for binding heparin to antithrombin III and the subsequent inhibition of clotting factors.

Iduronic acid also participates in the regulation of cell growth and differentiation. It interacts with growth factors and cytokines. For example, iduronic acid binds to fibroblast growth factor-2, enhancing the activity of the protein and promoting cell proliferation.

This compound is also important in tissue engineering. As iduronic acid is a component of various glycosaminoglycans such as heparan sulfate and dermatan sulfate, which are essential for the formation of extracellular matrix in the tissues, it helps in tissue engineering to enhance the properties of synthetic extracellular matrices, like biocompatibility. Mechanical strength and the ability to support cell growth.

Iduronic acid has applications in the field of biotechnology too. They are helpful in the production of biopharmaceuticals such as fusion proteins, growth factors, and monoclonal antibodies. In the food industry, iduronic acid acts as a food additive and a flavour enhancer. In the field of veterinary medicine, it helps as a treatment for joint disorders. It is also useful in research to study the structure and function of glycosaminoglycans, especially heparin sulfate.

Difference Between Glucuronic Acid and Iduronic Acid

Definition

Glucuronic acid is a type of uronic acid with the molecular formula C₆H₁₀O₇ having a carboxyl group attached to the first carbon atom, while iduronic acid is another type of uronic acid with the molecular formula C₆H₁₀O₇  having a carboxyl group attached to the second carbon atom.

Structure

Glucuronic acid has a carboxyl group on the first carbon atom (C1), whereas iduronic acid has a carboxyl group on the second carbon atom (C2).

Component of

Glucuronic acid is a major component of hyaluronic acid and chondrin sulfate, whereas iduronic acid is a component in heparan sulfate dermatan sulfate.

Acidity

Glucuronic acid is less acidic, while iduronic acid is more acidic than glucuronic acid.

Medical Applications

Glucuronic acid helps in the production of different drugs and biopharmaceuticals, such as monoclonal antibodies, anticoagulants, and detoxification of drugs and toxins, while iduronic acid helps in the production of anticoagulants such as heparin, and in tissue engineering to enhance the properties of synthetic extracellular matrix materials such as biocompatibility and mechanical strength.

Conclusion

Glucuronic acid and iduronic acid are two different types of uronic acids. Glucuronic acid has a carboxyl group on the first carbon atom (C1), whereas iduronic acid has a carboxyl group on the second carbon atom (C2). This structural difference between glucuronic acid and iduronic acid gives them different properties and uses.

Reference:

1. “Glucuronic acid” Green Facts.
2. “CHEBI:24769 – iduronic acid” ChEBI.

Image courtesy:

1. “Glucuronic acid” By DoSiDo – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Iduronic Acid” By Michał Sobkowski – Own work (CC BY-SA 3.0) via Commons Wikimedia