Table 1.
Kinetic parameters for the decarboxylation of truncated substrates catalyzed by yeast OMPDC and for activation by phosphite dianion at 25 °C.a
| EO | FEO | Orotidine | 5′-dFO | |
|---|---|---|---|---|
| (kcat/Km)Eb (M−1 s−1) |
0.026 c | 10 | 1.8 × 10−4 d | 0.078 |
| (kcat/Km)E·HPi/Kd
e (M−2 s−1) |
1.2 × 104 f | 4.8 × 104 | 9.3 × 10−3 g | 16 |
| Activation by 1 M HPO32− |
5 × 105-fold | 5 × 103-fold | 50-fold | 200-fold |
| Intrinsic Phosphite Binding Energy (kcal/mol) |
7.7 | 5.0 | 2.3 | 3.2 |
a
At pH 7.0 and I = 0.14 (NaCl), unless noted otherwise.
b
Second-order rate constant for the unactivated OMPDC-catalyzed decarboxylation of the truncated substrate in the absence of phosphite. The estimated error is ± 10%.
c
Data from Ref. 13.
d
At pH 7.1.
e
Third-order rate constant for the phosphite-activated OMPDC-catalyzed decarboxylation of the truncated substrate. The estimated error is ± 20%.
f
Data from Ref. 11.
g
At pH 7.1 and I = 0.21 (NaCl).