Table 1.

Comparison of the inhibition by methotrexate, trimethoprim, and EGCG of dihydrofolate reductase activity

Enzyme sourceInhibitorKI (nmol/L)k3 (min−1)k4 (min−1)k3/k4 (ratio)KI* (pmol/L)
Bovine liverEGCG1090.130.00432.53,253
ECG51.30.110.0157.36,156
Chicken liverEGCG10,300
Methotrexate1.32.90.0201458.9
Trimethoprim3,530
Escherichia coliMethotrexate3.66.90.026265.413.5
Trimethoprim0.492.00.08623.320.2
Streptococcus faeciumMethotrexate235.10.013392.358.5
Trimethoprim4.62.10.583.61,000
  • NOTE: Values for the inhibition of DHFR from different sources by methotrexate and trimethoprim were obtained from the literature (7). The values of KI, KI*, k3, and k4 for EGCG were calculated at pH 8.02.