Table 2. Kinetic Parameters for MgTNP-ATP Activation of the Pyruvate Carboxylation Reaction Catalyzed by RePC in the Presence of Different Concentrations of l-Aspartate^a.

[l-aspartate] (mM)	Ka for MgTNP-ATP (μM)	kcat (s–1)	k0 (s–1)
0	16.1 ± 2.9	2.1 ± 0.1	0.48
2	33.5 ± 5.6	1.9 ± 0.1	0.43
4	39.1 ± 6.2	1.6 ± 0.1	0.23
8	85.1 ± 17.6	1.5 ± 0.3	0.16

^aAssay conditions: 0.1 M Tris-HCl (pH 7.8), 20 mM NaHCO₃, 6 mM MgCl₂, 1 mM MgATP, 0.2 mM NADH, 10 mM sodium pyruvate, and 5 units of malate dehydrogenase (MDH). The concentrations of MgTNP-ATP and l-aspartate were varied from 0 to 100 μM and from 0 to 8 mM, respectively. The parameters (±standard errors) except k₀, which was measured directly, were estimated from a nonlinear regression fit of the data at each l-aspartate concentration to eq 1, where h₁ was set to 2.3, the value determined previously.¹³