Table 5.
Effect of acetyl-CoA on the coupling of the HCO3−-dependent ATPase reaction in the BC domain to pyruvate carboxylation in the CT domaina.
| (+) acetyl-CoA | (−) acetyl-CoA | ||
|---|---|---|---|
| Pi releasec |
% of (+) acetyl-CoAb |
||
| kcat (min−1) | 290 ± 5 | 16.9 ± 0.8 | 5.8 |
| Ka pyruvate (mM) | 0.16 ± 0.01 | 0.048 ± 0.008 | 30 |
| kcat/Ka (min−1 mM−1) | 1820 ± 10 | 350 ± 15 | 19 |
| Oxaloacetate formation | |||
| kcat (min−1) | 310 ± 8 | 1.52 ± 0.03 | 0.5 |
| Km pyruvate (mM) | 0.65 ± 0.05 | 0.013 ± 0.002 | 2 |
| kcat/Km (min−1 mM−1) | 470 ± 15 | 115 ± 5 | 24 |
a
Initial rates of Pi release and oxaloacetate formation were determined as detailed in the methods section both in the presence and absence of 0.25 mM acetyl-CoA at varying concentrations of pyruvate (0.03-5.25 mM) and 15 mM HCO3−.
b
Percentage of parameters determined without acetyl-CoA compared to those determined with acetyl-CoA.
c
Kinetic parameters were determined from fits of the data to eqn (1).