Table 2. Kinetic parameters a for cytochrome c reductase with pea ferredoxin, E. coli flavodoxin, and E. coli ferredoxin, and the melting temperatures of thermal unfolding transitions for Xac-FNR, pea-FNR and Ec-FNR b.
| pea ferredoxin | E. coli ferredoxin | E. coli flavodoxin | ||||||||
| FNR | Km (µM) | kcat (s−1) | kcat/Km (µM−1s−1) | Km (µM) | kcat (s−1) | kcat/Km (µM−1s−1) | Km (µM) | kcat (s−1) | kcat/Km (µM−1s−1) | TM (°C) c |
| Xac-FNR | <0.1 d | <0.1 d | Nd e | <0.1 d | <0.1 d | Nd e | <0.1 d | <0.1 d | Nd e | 48.1±0.8 |
| pea-FNR | 2.2±0.2 f | 75.0±0.5 f | 34.1 f | Nd e | Nd e | Nd e | Nd e | Nd e | Nd e | 61.5±0.5 |
| Ec-FNR | 1.4±0.1 f | 22.8±0.2 f | 16.3 f | 0.074±0.023 f | 12.3±1.2 f | 164.9 f | 2.3±0.2 f | 8.9±1.0 f | 3.9 f | 57.5±0.7 |
a
Each value represents the average of three independent determinations. A description of the calculation methods that were employed and the activity determinations are reported in the Materials and Methods. The original data are depicted in Figure S3.
b
Cytochrome c reduction was determined at 550 nm (ε550 = 19 mM−1 cm−1) as described in the Materials and Methods.
c
TM is the temperature of the midpoint of the thermal denaturation transition and was determined as described in the Materials and Methods.
d
An estimate of the limit of the determination based on the tested sensitivity of the method.
e
Not determined.
f
Values of parameters for pea-FNR and Ec-FNR were obtained from a reference [49].