5-Hydroxyisourate

5-Hydroxyisourate (5-HIU) is a metabolite involved in the purine metabolism pathway. It is an intermediate product in the breakdown of adenine and guanine, two of the four nucleobases in DNA and RNA.

Metabolism

5-Hydroxyisourate is produced from uric acid by the enzyme uricase, also known as urate oxidase. This reaction is part of the purine degradation pathway, which is responsible for the breakdown and recycling of purine nucleobases.

Following its formation, 5-HIU is further metabolized by the enzyme 5-hydroxyisourate hydrolase to produce 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline (OHCU). This reaction is the second step in the three-step enzymatic process that converts uric acid to S-(+)-allantoin, a more soluble and easily excreted compound.

Clinical significance

Abnormal levels of 5-Hydroxyisourate can be indicative of disorders related to purine metabolism, such as gout and Lesch-Nyhan syndrome. In gout, the overproduction or under-excretion of uric acid leads to the formation of urate crystals in the joints, causing inflammation and pain. Lesch-Nyhan syndrome, on the other hand, is a genetic disorder characterized by the overproduction of purines, leading to an excess of uric acid and a variety of neurological symptoms.

See also

• Purine metabolism
• Uric acid
• Gout
• Lesch-Nyhan syndrome