A young man with leukemia is treated with methotrexate. Which of the following is the mechanism of action of this drug?
(A) preventing absorption of folic acid
(B) inhibiting dihydrofolate reductase
© preventing formation of messenger
ribonucleic acid (mRNA)
(D) forming a cytotoxic metabolite
(E) preventing proper functioning of
membrane adenosine triphosphatase
(ATPase)
solution
(B) The most likely mode of action of methotrexate is by tightly binding dihydrofolate reductase
(DHFR), which maintains the intracellular folate pool in its fully reduced form as tetrahydrofolates.
These compounds are required in the de novo synthesis of pyrimidines and purines.