Thiouric acid

Thiouric acid is a chemical compound that is a sulfur analog of uric acid. It is a product of the metabolism of thiopurine drugs, which are used in the treatment of leukemia and autoimmune diseases. Thiouric acid is formed in the body by the action of an enzyme called xanthine oxidase.

Chemical Structure and Properties

Thiouric acid has the chemical formula C5H4N4OS. It is a tautomeric compound, meaning it can exist in two or more structural forms that are in rapid equilibrium. The two tautomeric forms of thiouric acid are the thione form and the thiol form. The thione form is more stable and is the form that is usually found in solution.

Thiouric acid is a weak acid, with a pKa value of 5.5. It is soluble in water and in polar organic solvents such as ethanol and dimethyl sulfoxide (DMSO).

Biological Role

In the body, thiouric acid is formed from the metabolism of thiopurine drugs such as azathioprine and mercaptopurine. These drugs are used in the treatment of leukemia and autoimmune diseases. The metabolism of these drugs is complex and involves several enzymes, including xanthine oxidase.

Thiouric acid is excreted in the urine. High levels of thiouric acid in the urine can be an indication of an overactive xanthine oxidase system, which can occur in certain diseases such as gout and Lesch-Nyhan syndrome.

Health Effects

The health effects of thiouric acid are not well understood. It is known that high levels of thiouric acid can cause crystalluria, which is the presence of crystals in the urine. This can lead to kidney damage if not treated. There is also some evidence that thiouric acid may have anti-inflammatory and immunosuppressive effects, which could potentially be harnessed for therapeutic purposes.

See Also

• Uric acid
• Thiopurine
• Xanthine oxidase