Table 2

Effects of chemical inhibitors on 5-FU formation catalyzed by human liver cytosol (samples HL-1 and HL-10)

Tegafur (1 mm) was incubated with human liver cytosol (2.5 mg/ml) in the absence or presence of chemical inhibitors. Results are presented as means of duplicate determinations. Values in parentheses indicate percentage of control activities.
5-FU formationbReported apparent Ki
ChemicalμmHLa-1HL-10dThdPase, μmUrdPase, μmReference
None17 (100)36 (100)
5-Chlorouracil1010 (59)17 (47)38 ± 811 ± 2 (22)
1004 (24)3 (8)
6-Benzyl-2-thiouracil1017 (100)34 (94)181 ± 95 >900 (22)
10016 (94)29 (81)
20013 (76)24 (67)
TPI0.017 (41)19 (53)0.017>1000 (17)
0.14 (24)5 (14)
14 (24)5 (14)
2,6-Dihydroxypyridine517 (100)33 (92)433 ± 773.4 ± 0.4 (22)
1014 (82)35 (97)
5005 (29)7 (19)
  • a HL, human liver (sample).

  • b pmol/min/mg protein.