Dj. Mauro et al., MECHANISMS OF EXCISION OF 5-FLUOROURACIL BY URACIL DNA GLYCOSYLASE INNORMAL HUMAN-CELLS, Molecular pharmacology, 43(6), 1993, pp. 854-857
Recent evidence indicates that 5-fluorouracil (5-FlUra) is incorporate
d into DNA and is removed by the DNA repair enzyme uracil DNA glycosyl
ase. Synthetic oligonucleotides containing either a single uracil or 5
-FlUra residue were constructed to examine the mechanisms by which hum
an cells remove 5-FlUra from DNA. The human uracil DNA glycosylase exc
ised uracil in a manner similar to that observed for the bacterial enz
yme. In contrast, a significant difference was observed in their abili
ties to remove 5-FlUra. In particular, both the bacterial an normal hu
man enzymes displayed 13-17-fold increases in their apparent K(m) valu
es but the apparent V(max) values remained virtually constant. These r
esults demonstrate that normal human cells possess a defined capacity
to remove 5-FlUra incorporated into DNA. However, specific kinetic dif
ferences may exist that affect their capacity to remove 5-FlUra formed
in DNA after treatment with this cancer chemotherapeutic agent.