Orotic acid, also known as pyrimidinecarboxylic acid, is a naturally occurring organic compound that plays a crucial role in the biosynthesis of nucleotides. It is an intermediate in the de novo synthesis of pyrimidine nucleotides, which are essential for the formation of DNA and RNA. Despite its name, orotic acid is not a true vitamin, but it is sometimes referred to as vitamin B13 due to its involvement in cellular metabolism.

Structure and Composition
Orotic acid has the chemical formula C5H4N2O4. It consists of a pyrimidine ring with two keto groups (carbonyl groups) and a carboxyl group, making it both acidic and highly polar. This structure allows orotic acid to participate in various biochemical reactions.

Biological Functions
Orotic acid is primarily known for its role in nucleotide synthesis, specifically in the production of pyrimidines:

Pyrimidine Biosynthesis: Orotic acid is a precursor in the biosynthesis of pyrimidine nucleotides, including uracil, cytosine, and thymine. These nucleotides are essential building blocks for DNA and RNA. Orotic acid is converted into orotidine-5'-monophosphate (OMP), which is then decarboxylated to produce uridine monophosphate (UMP), a key pyrimidine nucleotide.
Cellular Growth and Division: Since pyrimidine nucleotides are necessary for the replication of DNA, orotic acid is indirectly involved in processes related to cellular growth and division. It plays a significant role in rapidly dividing cells, such as those in the immune system, gastrointestinal tract, and during development.
Medical and Health Applications
While orotic acid itself is not commonly used as a therapeutic agent, it has been studied for its potential health benefits and medical relevance:

Cardioprotective Effects: Some studies suggest that orotic acid, in the form of orotate salts, might have a role in supporting heart health by improving energy metabolism in cardiac tissues, particularly in conditions like heart failure. Magnesium orotate and potassium orotate have been explored for these effects.
Nutritional Support: Orotic acid is sometimes included in supplements, especially in sports nutrition, due to its potential to support energy production and cellular repair, although its effectiveness is still under research.
Disorders Related to Orotic Acid
Certain metabolic disorders can involve abnormal levels of orotic acid, leading to health issues:

Orotic Aciduria: A rare genetic disorder in which there is a deficiency of the enzyme uridine monophosphate synthase (UMPS), leading to the buildup of orotic acid in the body. This condition can result in megaloblastic anemia and growth retardation. Treatment often involves supplementation with uridine, which bypasses the defective pathway.
Liver Disease and Urea Cycle Disorders: Elevated levels of orotic acid can be observed in individuals with urea cycle disorders, where ammonia builds up in the body due to defective processing. Orotic acid accumulation is used as a diagnostic marker in these cases.
Industrial and Research Applications
Orotic acid has applications beyond the biological field:

Laboratory Research: In scientific research, orotic acid is often used as a biochemical tool to study nucleotide metabolism and the regulatory mechanisms of pyrimidine biosynthesis.
Food Additive: In some cases, orotic acid is used in the animal feed industry as a growth promoter, particularly for enhancing liver function and overall growth in livestock.
Conclusion
Orotic acid is a critical intermediate in pyrimidine nucleotide biosynthesis, linking it to fundamental cellular processes such as DNA and RNA formation. Its role in health and disease, particularly in metabolic disorders like orotic aciduria, underscores its biological importance. While not a true vitamin, its involvement in energy metabolism and nucleotide production makes it a compound of interest in both biochemical research and potential therapeutic applications.