Table 3.

Apparent kinetic parameters of ZmPEPC-C₄ wildtype and mutant S100K enzymes

Parametera	Wildtype	S100K
Saturation by total PEP
Vmax	19.9 ± 0.8	13.4 ± 0.4
S0.5	17.5 ± 1.3	4.6 ± 0.5
h	1.6 ± 0.1	1.8 ± 0.3
Saturation by G6Pb
v0	5.4	12.6
vamax	22.7 ± 0.2	13.1 ± 0.8
A0.5	3.4 ± 0.1	0.9 ± 0.1
h	1.4 ± 0.0	1.8 ± 0.5
Saturation by G6P + 20 mm malateb
v0	0.01	2.2
va max	NE	13.9 ± 0.7
A0.5	NE	5.9 ± 0.7
h	NE	1.0 ± 0.0
Saturation by malateb
v0	6.9	14.4
vi min	2.21	7.6
I50	0.23 ± 0.0	1.0 ± 0.01
h	1.3 ± 0.1	4

^a Values ±S.D. were estimated by the best fit to Equation 2 for saturation by total PEP, to Equation 1 for saturation by G6P in the absence and presence of malate, or to Equation 3 for saturation by malate; v₀ was fixed to the experimentally determined values. Velocities (v₀, V_max, v_{a max}, and v_{i min}) are given as units/mg of protein and S_0.5, A_0.5, and I_0.5 are given as mm. Assays were carried out at pH 7.3, 0.4 mm free Mg²⁺, and 0.1 mm bicarbonate.

^b The apparent kinetic parameters for the allosteric effectors were determined at fixed 3 mm total PEP. NE, values not estimated due to the low enzyme activity under these conditions.