TABLE 1

Summary of the kinetic parameters measured for the hydrolysis of bambuterol and bambuterol monocarbamate enantiomers by human BChE

Data are expressed as mean (S.E.).

Tested CompoundExperimental Approach (Temperature)
As Inhibitors (37°C)As Substrates (30°C)
kIa (× 106 M−1min−1)IC50b (nM)k3 (min−1)kI1 (× 106 M−1min−1)kI2 (× 106 M−1min−1)k3 (min−1)
rac-BMB8.30 (0.17)3.9 (0.6)0.01175 (0.0003)3.88 (0.90)c0.255 (0.071)c0.0064 (0.0004)
R-BMB13.20 (0.74)2.7 (0.6)10.3 (6.9)0.482 (0.305)
S-BMB3.23 (0.12)8.7 (0.9)1.56 (0.26)0. 091 (0.030)
rac-MONO0.341 (0.019)44.7 (4.4)0.298 (0.183)c
R-MONO0.839 (0.015)23.4 (2.8)0.544 (0.258)
S-MONO0.215 (0.021)65.1 (9.6)0.127 (0.008)
  • a These kI values are referred to as kI1 when the tested compound is bambuterol (BMB) and kI2 when it is bambuterol monocarbamate (MONO).

  • b Calculated from data measured after 60 min of incubation.

  • c Data obtained by using the simple hydrolysis model, which does not consider the kinetic competition between the two enantiomers (see Fig. 2A).