TABLE 3.
Kinetic parameters of HCS and H72L mutant
| Enzyme |
Km |
kcat | Ki for lysine | |
|---|---|---|---|---|
| α-KG | Acetyl-CoA | |||
| μm | min−1 | μm | ||
| HCSa | 5.4 ± 0.7 | 10.9 ± 0.4b | 70.7 ± 6.1 | |
| 33 ± 5.3 | 41 ± 4 | |||
| H72La | 174 ± 13 | 14.9 ± 0.5b | >2000c | |
| 37 ± 4.2 | 31 ± 1 | |||
a Recombinant enzymes with N-terminal His8 tags were used.
b kcat for α-KG is lower than that for acetyl-CoA because HCS and the mutants are significantly subject to substrate inhibition by acetyl-CoA.
c The H72L mutant was significantly desensitized to feedback inhibition, and 50% inhibition was not achieved even in the presence of 2,000 μm lysine.