Table 1.

Nucleoside	kcat (s−1) values
	WT	S74E	Ratio S74E/WT	S74D	S74Q	S74A
(a) Catalytic activities of wild-type dCK and dCK phosphorylation site Ser-74 dCK mutants
dC	0.04 ± 0.005	0.45 ± 0.03	11.25	0.16 ± 0.003	0.04 ± 0.03	0.04 ± 0.003
dA	0.77 ± 0.07	0.69 ± 0.04	0.90	1.00 ± 0.07	0.90 ± 0.08	1.12 ± 0.10
dG	0.73 ± 0.05	0.36 ± 0.01	0.49	0.57 ± 0.05	0.65 ± 0.03	0.68 ± 0.04
dFdC	0.44 ± 0.03	1.21 ± 0.05	2.75	0.90 ± 0.02	0.45 ± 0.06	0.50 ± 0.03
AraC	0.32 ± 0.02	1.06 ± 0.04	3.31	0.57 ± 0.02	0.30 ± 0.08	0.33 ± 0.05

	KM (μM)		kcat/KM (M−1 s−1)
	WT	S74E	WT	S74E
(b) Steady-state kinetic parameters KM and kcat/KM of dCK WT and dCK(S74E)
dC	1.7 ± 0.2	8.9 ± 0.3	23.1 × 103	50.6 × 103
dA	116.9 ± 11.5	517.9 ± 92.7	6.6 × 103	1.3 × 103
dG	245.8 ± 18.8	601.8 ± 80.2	2.9 × 103	0.6 × 103
dFdC	6.2 ± 1.3	15.0 ± 3.1	71.0 × 103	80.7 × 103
AraC	5.9 ± 1.5	24.1 ± 12.1	54.2 × 103	44.0 × 103

All kinetic measurements were performed at 25 °C with 2 mM ATP as the phosphoryl donor and, as indicated, with different nucleoside substrates.

Calculated k_cat values include standard error (n = 4).

K_M values were determined with constant 2 mM ATP and varying concentrations of substrates. All measurements were performed at 25 °C. The K_M values are an average of at least three experiments and were calculated using Origin (Hyperbolic function). The k_cat values from Table 1a were used to calculate the k_cat/K_M values presented here.