Table 2.
Kinetic Parameters for HiSAT Wild-Type and Mutant Enzymes at pH 7.3
| V1/Et (s−1) | V1/KSerEt (M−1 s−1) | V1/KAcCoAEt (M−1 s−1) | KAcCoA (mM) | KSer (mM) | |
|---|---|---|---|---|---|
| wild typea | 360 ± 10b | (7.53 ± 0.07) × 104 | (5.1 ± 0.8) × 105 | 0.7 ± 0.1 | 4.7 ± 0.4 |
| H154N | 0.29 ± 0.02 | 470 ± 80 | 1300 ± 400 | 0.21 ± 0.08 | 0.6 ± 0.1 |
| (fold change) | −(1240 ± 90)c | −(160 ± 30) | −(390 ± 140) | −(3 ± 1) | −(8 ± 1) |
| H189N | 18.7 ± 0.9 | 590 ± 70 | N/Ad | N/A | 32 ± 4 |
| (fold change) | −(19 ± 1) | −(130 ± 20) | +(7 ± 1) | ||
| D139N | 34 ± 1 | 200 ± 10 | (2.7 ± 0.4) × 105 | 0.12 ± 0.02 | 160 ± 10 |
| (fold change) | −(10.6 ± 0.4) | −(380 ± 20) | −(1.9 ± 0.4) | −(6 ± 1) | +(34 ± 4) |
| H154N/H189N | 0.0152 ± 0.0004 | 0.57 ± 0.03 | 64 ± 3 | 0.24 ± 0.02 | 27 ± 2 |
| (fold change) | −(23700 ± 900) | −(132000 ± 7000) | −(8000 ± 1000) | −(2.9 ± 0.5) | +(5.7 ± 0.6) |
a
From Johnson et al. (6).
b
Values are ±SE.
c
The symbols, − and +, represent decrease and increase, respectively.
d
N/A is not applicable; KAcCoA is zero in an equilibrium kinetic mechanism.