A 63-year-old woman comes to the physician for a follow-up examination. She has metastatic breast cancer treated with cyclophosphamide and fluorouracil. Thymidylate synthase, which is required for deoxynucleotide synthesis, is one target of fluorouracil. Which of the following is a substrate for thymidylate synthase?

Question

Quizplus · Accepted Answer

Thymidylate synthase catalyzes the conversion of dUMP (deoxyuridine monophosphate) to dTMP (deoxythymidine monophosphate), making dUMP the substrate for this enzyme.  The de novo pathway to dTTP synthesis first requires the use of dUMP from the metabolism of either UDP or CDP. The dUMP is converted to dTMP by the action of thymidylate synthase.

A 63-Year-Old Woman Comes to the Physician for a Follow-Up