2015 Folate, Vitamin B12 and Inhibitors

Answer to example question 3

Trimetrexate (an antibiotic) is an inhibitor of dihydrofolate reductase (not thymidylate synthase), therefore A is incorrect. Approximately a 5 year supply of vitamin B12 is stored; folate stores are much lower (~1-6 months), therefore there is a higher daily requirement of folate (C is incorrect). The effects of deficiency were reversed:  folate deficiency is a cause of birth defects; vitamin B12 deficiency is associated with irreversible CNS defects in the elderly (D is incorrect).  Intrinsic factor is required for absorption of vitamin B12, not folate (E is incorrect).  Vitamin B12 is responsible for the mobilization of TH<sub>4</sub>; B is correct.

Email: Dr. Janet Fitzakerley | ©2015 University of Minnesota Medical School Duluth | Last modified: 4-may-15 9:28 PM