DHFR (Dihydrofolate Reductase) is an enzyme that holds a crucial role in DNA synthesis and repair. It catalyzes the conversion of dihydrofolate into tetrahydrofolate, an essential cofactor for the production of 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.