Tables

- Enzymology of Methylation of Tea Catechins and Inhibition of Catechol-O-methyltransferase by ()-Epigallocatechin Gallate

TABLE 1
Kinetic parameters of EGCG and EGC methylation by liver cytosolic COMT

Kinetic studies were conducted for 2 min (EGCG) or 5 min (EGC) using 1 mg/ml of liver cytosolic proteins in the presence of 50 µM SAM. The kinetic parameters (K_m and V_max) were calculated from duplicated determinations with GraphPad Prism. Values represent best-fit values ± standard error.

TABLE 2
Median inhibition concentration (IC₅₀) of the inhibition of methylation of EGC and L-DOPA by catechins and their derivatives

Studies on the inhibition of EGC methylation were conducted for 10 min using 1 mg/ml of liver cytosolic proteins in the presence of 10 µM EGC, 50 µM SAM and different concentrations of inhibitors. Studies on the inhibition of L-DOPA methylation were conducted for 30 min using 25 units of porcine liver COMT in the presence of 100 µM L-DOPA, 60 µM SAM and different concentrations of inhibitors. Values of IC₅₀ (µM) were calculated from duplicate determinations and represent the concentrations of inhibitor that inhibited the formation of 4'-MeEGC or 3-MeDOPA by 50%.