TABLE 2.
Affinity of terminal oxidases for oxygena
| Terminal oxidaseb | Oxygen electrode |
Myoglobin |
Leghemoglobin |
|||
|---|---|---|---|---|---|---|
| Km (μM) | Vmax (nmol/min/mg) | Km (μM) | Vmax (nmol/min/mg) | Km (nM) | Vmax (nmol/min/mg) | |
| bo3 | 3.2 ± 1.3 | 117 ± 14 | 0.25 ± 0.04 | 92 ± 13 | NDc | ND |
| CIO | 4.0 ± 2.1 | 213 ± 34 | 0.41 ± 0.10 | 130 ± 34 | ND | ND |
| aa3 | 4.3 ± 1.0 | 91 ± 38 | ND | ND | ND | ND |
| cbb3-1 | 0.25 ± 0.02 | 77 ± 30 | 0.044 ± 0.022 | 51 ± 15 | 6.6 | 7.7 |
| cbb3-2 | 0.23 ± 0.08 | 82 ± 35 | 0.032 ± 0.021 | 53 ± 25 | 6.5 | 8.5 |
a
The Km values for oxygen were determined using an oxygen electrode or deoxygenation kinetics of oxymyoglobin or oxyleghemoglobin. Values for the oxygen electrode and myoglobin methods are presented as means ± standard deviations of results from at least three independent experiments. Values for the leghemogbobin method were determined from only one experiment.
b
Membrane fractions of the strains QXBo, QXCi, QXAaS2, QXCb1, and QXCb2 were used for determination of the oxygen affinity of bo3, CIO, aa3, cbb3-1, and ccb3-2 oxidases, respectively.
c
ND, not determined.