DHFR (Dihydrofolate Reductase) is an enzyme that plays a crucial role in DNA synthesis and repair. It catalyzes the conversion of dihydrofolate to tetrahydrofolate, an essential cofactor for producing purines, thymidylate, and certain amino acids. This process is vital for cell growth and division, making DHFR a key target in cancer treatment, where inhibitors such as methotrexate block its activity to stop rapidly dividing cells.