Inhibition of Dihydrofolic Reductase by Aminopterin and Amethopterin.
The enzyme, dihydrofolic reductase, which catalyzes the TPNH-linked reduction of dihydrofolic acid to tetrahydrofolic acid, is inhibited non-competitively by the folic acid antagonists, Aminopterin and Amethopterin. Values of 1 × 10 -9 M and 2.3 × 10 -9 M were obtained for the inhibitor constants (K I ) of Aminopterin and Amethopterin, respectively.