Dihydrofolate reductase

Dihydrofolate reductase (PDB , EC 1.5.1.3), or DHFR, reduces dihydrofolic acid to tetrahydrofolic acid, which can be converted to the kinds of tetrahydrofolate cofactors used in 1-carbon transfer chemistry.

A variety of drugs act on dihydrofolate reductase, including the antibiotic trimethoprim, the antimalarial drug pyrimethamine, and the chemotheraputic agent methotrexate. The first anticancer drug, aminopterin, also acts on this enzyme, binding some 1000 times more tightly to the enzyme than folate itself.