Metabolism USMLE Step 1 Practice Question
Methotrexate is used as therapy for rheumatoid arthritis, but has many side effects related to competitive inhibition of the enzyme dihydrofolate reductase. These side effects can be decreased without interfering with the efficacy of methotrexate by ingestion of additional folate. If patients treated with methotrexate are given sufficient folate, which of the following would most likely occur?
Answer choices
- ADihydrofolate reductase will increase its affinity for methotrexate
- BDihydrofolate reductase will have a higher apparent Km for dihydrofolate
- CDihydrofolate reductase will reach the same Vmax as it would in the absence of methotrexateCorrect answer
- DDihydrofolate reductase will have a higher Vmax than it would in the absence of methotrexate
- EDihydrofolate reductase will have a lower apparent Km for dihydrofolate
- FFolic acid supplementation restoring dihydrofolate reductase substrate availability
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