Deficiency of which of the following enzyme leads to toxicity of 5-fluorouracil?: (A) Purine nucleoside phosphorylase, (B) Dihydropyrimidine dehydrogenase, (C) PRPP synthase, (D) Adenosine deaminase
Answer is B. 5-fluorouracil is acted upon by dihydropyrimidine dehydrogenase - Deficiency - accumulation of 5-FU - toxicity.