Table 3.
Steady-State Kinetic Parameters for Binding and Oxidative Decarboxylation of Alternate Substrates in W138F Mutantsa
| D- glutamate |
L-glutamate | AIB | ||||||
|---|---|---|---|---|---|---|---|---|
| Kib (mM) |
kcat (s−1) |
KL-glu (mM) |
kcat/KL-glu (M−1s−1) |
kcat (s−1) |
KAIB (mM) |
kcat/KAIB (M−1s−1) |
Ratio kcat/KL-glu: kcat/KAIB |
|
| W138F/M141R | 89 (10) | 0.0022 (0.0003) |
270 (74) |
0.008 (0.002) |
0.0040 (0.0002) |
41 (5) |
0.10 (0.01) |
0.08 |
| W138F | 4 × 10−6c | 0.179 (0.007) |
37 (4) |
4.8 (0.6) |
||||
| WT | > 500 | 6 × 10−6c | 480d (40) |
8 × 10−6 | 17.7e (0.5) |
2.2e (0.2) |
8000e (800) |
1 × 10−9 |
a
Errors are given in parentheses.
b
Ki was determined assuming competitive inhibition against AIB in the AIB decarboxylation reaction.
c
Based on the total absorbance change observed in the SSDH end-point assay.
d
The Km value reported is the Ki obtained assuming competitive inhibition against AIB.
e
Data for WT AIB decarboxylation taken from (17).