Mammalian dihydropyrimidine dehydrogenase

Area of Science:

• Biochemistry
• Enzymology
• Drug Metabolism

Background:

• Dihydropyrimidine dehydrogenase (DPD) is a key enzyme in pyrimidine catabolism.
• DPD utilizes a complex cofactor set, including flavins (FAD, FMN) and iron-sulfur clusters.
• DPD processes the anticancer drug 5-fluorouracil, impacting treatment efficacy.

Purpose of the Study:

• To elucidate the precise catalytic mechanism of DPD.
• To identify the active cofactor state of DPD.
• To understand DPD's role in 5-fluorouracil metabolism.

Main Methods:

• Biochemical assays to characterize enzyme activity.
• Spectroscopic methods to analyze cofactor states.
• Kinetic studies to determine rate-limiting steps.

Main Results:

• The active form of DPD features a FAD-4(Fe4S4)-FMNH2 cofactor set.
• The catalytic cycle initiates with pyrimidine substrate reduction.
• NADPH oxidation at FAD is followed by electron transfer to reinstate FMNH2.

Conclusions:

• The identified active state simplifies mechanistic possibilities for DPD.
• The study clarifies the sequence of electron transfer and cofactor re-oxidation.
• Understanding DPD's mechanism is vital for optimizing chemotherapy involving 5-fluorouracil.