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Subcellular localization of dihydropyrimidine dehydrogenase
A B Van Kuilenburg1, H Van Lenthe, R J Wanders
1Academic Medical Center, University of Amsterdam, Emma Children's Hospital, The Netherlands.
Biological Chemistry
|November 5, 1997
Summary
Dihydropyrimidine dehydrogenase (DPD) is primarily found in the cytosol of rat liver cells. This study used differential centrifugation and density gradient centrifugation to confirm the exclusive cytosolic localization of DPD activity.
Area of Science:
- Biochemistry
- Cell Biology
- Enzymology
Background:
- Dihydropyrimidine dehydrogenase (DPD) is an enzyme involved in pyrimidine metabolism.
- Previous studies have reported conflicting data regarding the subcellular localization of DPD in mammalian liver tissues.
Purpose of the Study:
- To definitively determine the subcellular localization of dihydropyrimidine dehydrogenase (DPD) in rat liver.
- To resolve conflicting data on DPD's cellular location using established biochemical fractionation techniques.
Main Methods:
- Rat liver homogenates were prepared and subjected to differential centrifugation to isolate subcellular fractions.
- Marker enzyme activities were measured in each fraction to confirm their purity.
- DPD activity was assayed in all fractions, with further analysis of the light mitochondrial fraction using equilibrium density gradient centrifugation.
Main Results:
- Almost all measured DPD activity was consistently found in the cytosolic fraction.
- Equilibrium density gradient centrifugation confirmed that DPD activity did not co-localize with any specific subcellular organelles.
- No significant DPD activity was detected in mitochondrial or microsomal fractions.
Conclusions:
- DPD in rat liver is exclusively localized in the cytosol.
- This finding clarifies previous discrepancies regarding DPD's subcellular distribution.
- The exclusive cytosolic localization has implications for understanding pyrimidine metabolism and drug catabolism in the liver.