A 63- year-old woman presents with a long history of joint pains. Physical examination reveals severely deformed fingers secondary to rheumatoid arthritis. The rheumatologist recommends Methotrexate. This drug inhibits which of the following conversions?
A. Dopamine to norepinephrine
B. Tyrosine to Dopa
C. Folate to dihydrofolate
D. Histidine to formiminoglutamate (FIGLU)
E. Nor epinephrine to Vanillylmandelic acid
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