TABLE 2.

Kinetic constants for dCTP incorporation

Values were calculated by fitting the data points to Michaelis-Menten equation using GraphPad Prism (version 5.0).

Enzyme	kcata	Kmb	kcat/Km
	s−1	μm
gp43c	0.61d	0.49	1.25
A	0.39	0.92	0.42
A/V781I	0.51	0.92	0.55
ABC	0.46	2.7	0.17
ABC/R784A	0.39	3.3	0.12
ABC/Q807A	0.50	3.6	0.14

^a k_cat is the enzyme turnover number that is calculated by normalizing the maximum velocity of the reaction to the enzyme concentration.

^b K_m is the substrate concentration at half-maximum velocity of the reaction.

^c The previously reported gp43 values for dCTP k_cat and K_m are 1.0 s⁻¹ and 0.57 μm, respectively (51).

^d Standard deviations were determined on the basis of at least three independent experiments and represent a maximum of 12% of the reported value.