TABLE 5.
Apparent steady-state kinetic parameters of ISPs for selected substituted benzoates in air-saturated buffer
| ISP | Substrate | KmA (μM) | kcat (s−1) | kcat/KmA (104 M−1 s−1) |
|---|---|---|---|---|
| αBβB | Benzoate | 38 (1) | 16.3 (0.3) | 43 (1) |
| 2-Methylbenzoate | 2,890 (240) | 2.1 (0.2) | 0.07 (0.01) | |
| 3-Methylbenzoate | 49 (3) | 5.3 (0.2) | 11 (2) | |
| 3-Chlorobenzoate | 94 (8) | 2.2 (0.1) | 2.3 (0.3) | |
| αTβTc | Benzoate | 15 (1) | 2.4 (0.1) | 16 (1) |
| 2-Methylbenzoate | 590 (60) | 1.6 (0.1)b | 0.3 (0.02)b | |
| 3-Methylbenzoate | 5.3 (0.3) | 2.9 (0.04) | 46 (3) | |
| 4-Methylbenzoate | 43 (3) | 2.25 (0.06) | 5 (1) | |
| 2-Chlorobenzoate | 1,200 (240) | 1.4 (0.1)b | 0.1 (0.01)b | |
| 3-Chlorobenzoate | 22 (2) | 1.03 (0.01) | 4.6 (0.5) | |
| 4-Chlorobenzoate | 83 (7) | 0.86 (0.03) | 1 (0.1) | |
| αTβB | Benzoate | 81 (7) | 1.3 (0.12) | 1.6 (0.1) |
| 2-Methylbenzoate | 410 (124) | 0.3 (0.02) | 0.09 (0.01) | |
| 3-Methylbenzoate | 38 (4) | 1.4 (0.06) | 3.6 (0.2) | |
| 4-Methylbenzoate | 73 (1) | 1.2 (0.16) | 1.7 (0.2) | |
| 2-Chlorobenzoate | 1,200 (22) | 0.3 (0.02) | 0.02 (0.005) | |
| 3-Chlorobenzoate | 20 (3) | 1.3 (0.05) | 7 (1) | |
| 4-Chlorobenzoate | 458 (96) | 1.47 (0.09) | 0.3 (0.06) | |
| αBβT | Benzoate | 110 (20) | 4.0 (0.2) | 3.6 (0.3) |
| 2-Methylbenzoate | 5,130 (390) | 2.7 (0.2) | 0.05 (0.01) | |
| 3-Methylbenzoate | 178 (2) | 2.4 (0.3) | 1.3 (0.1) | |
| 3-Chlorobenzoate | 281 (38) | 3.1 (0.1) | 1.1 (0.1) |
a
Experiments were performed with 0.1 M air-saturated sodium phosphate (pH 7.0 at 25°C) containing 430 μM NADH. Standard errors are given in parentheses. ht-REDs were paired with the α subunit of the ISP. In these assays, αBβB and αBβT displayed no detectable activity in the presence of p-toluate, 2-chlorobenzoate, or 4-chlorobenzoate.
b
Values were based on O2 consumption to be consistent with the other values in the table. Values calculated based on benzoate consumption were at least one order of magnitude lower.
c
Values published in reference 20.