Table 1.
Rate constants for reactions of organophosphorylated AChE and their solvent D2O isotope effects.
| Phosphoryl Substituents | Reaction | k (10−6 min−1) H2O a | k (10−6 min−1) D2O | n | k H2O/k DO b |
|---|---|---|---|---|---|
| Dimethyl- | Aging (kA) | 1500 ± 500 | 1400 ± 500 | 2 | 1.1 ± 0.1 |
| Diethyl- | 39 ± 7 c | 41 ± 4 c | 1 | 1.0 ± 0.2 | |
| Dimethyl- | Hydrolysis (kH) | 6000 ± 530 | 3100 ± 360 | 2 | 1.9 ± 0.1 |
| Diethyl- | 83 ± 12 | 41 ± 5 | 3 | 2.0 ± 0.1 | |
| Dimethyl- | 2-PAM reactivation (kR) | 120,000 ± 6000 | 61,000 ± 4000 | 2 | 1.96 ± 0.04 |
| Diethyl- | 23,000 ± 1500 | 15,000 ± 300 | 2 | 1.68 ± 0.14 |
a Values listed for rate constants k in H2O are means of n experiments with the standard error of the mean. Since each entry in this table included paired measurements in H2O and D2O, n values were always the same for both solvents. b The solvent D2O isotope effect was the ratio of a rate constant in H2O to that in D2O. It was the unweighted average of the isotope effects from the n experiments calculated individually for paired H2O and D2O reactions in each experiment. When n = 1, the standard error was determined from the combined errors of the H2O and D2O fits to Equation (3). c When n = 1, the standard error was determined from the error of the fit to Equation (3). However, the overall errors in kA for diethylphosphorylated AChE depend much more on the values of kX and kH than on replicate values of kA (see Section 2.5), and therefore replicate values of kA for these species were not made.