Table 1.
Catalytic parameters for E. globulus and Nicotiana tabacum (tobacco) Rubisco at 25 °C
Values (±SD) are the average of the number of biological replicates (n) indicated (see the Materials and methods for more detail). The oxygention rate (kcato) was calculated using the equation Sc/o=(kcatc/Kc)/(kcato/Ko). Γ*, the CO2 compensation in the absence of mitochondrial respiration (Rd), was calculated as =0.5×[O2]c/Sc/o, where [O2]c is the O2 concentration in the chloroplast. Values used for fitting the A–Ci curves (Table 3; Fig. 2) were converted into the gas phase using the solubility constants for CO2 (0.0334 M M–1 bar–1) and O2 (0.00126 M M–1 bar–1) at 25 oC. CE and OE are the derived carboxylation and oxygenation efficiencies, respectively.
| Eucalyptus globulus | Nicotiana tabacum | |
|---|---|---|
| K m (CO2) at 0% O2, Kc0%O2 (µM) | 9.8 ± 0.3 (293 µbar) | 9.4 ± 0.1 |
| K m (CO2) at 21% O2, Kc21%O2 (µM) | 21 (629 µbar) | 19.5 |
| k cat c (s–1) | 3.0 ± 0.2 (n=6) | 3.1 ± 0.2 (n=19) |
| K i (O2), K o (µM) | 220 ± 18 (175 mbar) | 236 ± 9 |
| S c/o (M M–1) (n=2) | 80.4 ± 0.9 (2131 bar bar–1) | 82.3 ± 0.3 |
| Γ* (µM) | 1.57 (48.6 µbar) | 1.54 |
| k cat o (s-1) | 0.94 | 0.83 |
| CE21% O2, kccatc/Km (CO2)21% O2 (mM–1 s–1) | 143 | 159 |
| OE, kocato/Ki (O2) (mM–1 s–1) | 3.8 | 4.0 |