Which enzyme Deficiency leads to serious side effects with 5FU

Ans. b. Dihydropyrimidine dehydrogenaseRef: Goodman Gilman 13th E/P 11825FU is metabolized by Dihydropyrimidine dehydrogenase in liver and other tissues including tumor cells.Deficiency of this enzyme in patients can lead to a decreased metabolism and increased toxicity of 5FU like severe diarrhea and shock leading to death as well.Deficiency of this enzyme can be diagnosed in lymphocytes by assays or by comparing ratio of 5FU to its metabolite in plasma.