Which of the following statements explains why methotrexate is effective as a cancer chemotherapeutic? A) it serves as an analog of p-aminobenzoic acid and block bacterial synthesis of folate B) acts as an inhibitor of dihydrofolate reductase, thus preventing production of tetrahydrofolate C) it acts as a suicide substrates for the enzyme dihydropteroate synthetase D) prevents the conversion of N⁵,N¹⁰-methenyl THF to N¹⁰-formyl THF which is required in 2 steps of the purine synthesis pathway E) both b and d are correct

Question

Quizplus · Accepted Answer

Methotrexate inhibits the enzyme dihydrofolate reductase, which is responsible for the conversion of dihydrofolate to tetrahydrofolate. Tetrahydrofolate is required for the synthesis of purines and pyrimidines, which are necessary for the growth and division of cancer cells. By blocking this enzyme, methotrexate prevents the production of tetrahydrofolate and ultimately inhibits cancer cell proliferation. Choice A refers to the mechanism of sulfonamides, Choice C is the mechanism of sulfonamide and trimethoprim combination, and Choice D refers to the inhibitory action of 5-fluorouracil. Choice E is a correct statement but not the best choice for this question.

Which of the Following Statements Explains Why Methotrexate Is Effective