Dihydropyrimidine Dehydrogenase (DPD) is an enzyme that plays a crucial role in the metabolism of pyrimidines, which are essential components of nucleic acids. It catalyzes the reduction of dihydropyrimidines to pyrimidines, facilitating the breakdown of uracil and thymine. This process is vital for maintaining proper cellular function and DNA synthesis. Deficiency in DPD can lead to severe side effects when patients are treated with certain chemotherapy drugs, such as 5-fluorouracil. This is because the body cannot effectively metabolize these medications, resulting in toxicity. Understanding DPD's function is important for personalized medicine and improving treatment outcomes.