Biochemistry

Question 1

Leflunomide

Answer 1

Inhibits dihydroorotate dehydrogenase

Blocks conversion of carbamoyl phosphate to orotic acid

Pyrimidine synthesis step

Question 2

Mycophenolate and Ribavirin

Answer 2

Inhibit IMP dehydrogenase

Blocks conversion of IMP to GMP

Purine synthesis step

Question 3

Hydroxyurea

Answer 3

Inhibits ribonucleotide reductase

Blocks conversion of UDP to dUDP

Pyrimidine synthesis step

Question 4

6-mercaptopurine and Azathioprine

Answer 4

Inhibit de novo synthesis of purine

Blocks conversion of PRPP to IMP

Question 5

5-FU

Answer 5

Inhibits thymidylate synthase which decreases deoxythymidine monophosphate (dTMP) because blocks conversion of dUMP to dTMP

Pyrimidine synthesis step

Question 6

Methotrexate (MTX), Trimethoprim (TMP), and Pyrimethamine

Answer 6

Inhibits dihydrofolate reductase

Meds in order: in humans, bacteria, and protozoa

Blocks conversion of DHF to THF

Pyrimidine synthesis step