Table 1.
Activation parameters from fitting kcat of ecTSase to the Eyring equation in the absence (w/o) and presence (w/) of 50 mM MgCl2.a
| TSase | ΔH‡ kcal/mol | -TΔS‡ at 25 °C kcal/mol | ΔG‡ kcal/mol |
|---|---|---|---|
| w/ Mg2+ | 3.4 ± 0.2 | 12.8 ± 0.2 | 16.2 ± 0.4 |
| w/o Mg2+b | 3.4 ± 0.1 | 13.9 ± 0.1 | 17.3 ± 0.2 |
a
The KIE experiments suggest that the hydride transfer is rate limiting for kcat under both conditions (see text below), thus, the steady-state kinetic experiments actually exposed the activation parameters of the hydride transfer step. The values of kcat are presented in Table S1 in SI.
b
Data are from Ref 26.