Table 1.

Kinetic parameters of RNA extension with rNTPs by hPolη using Mg²⁺ or Mn²⁺ as cofactors.

Templating Nucleotide	Incoming Nucleotide	Cation	kcat (min−1)	Km (µM)	kcat/Km (min−1µM−1)	Relative Efficiency a	1/Relative Efficiency b
T	rATP	Mn2+	0.30 ± 0.01	5.9 ± 0.7	5.2 × 10−2	-	1
	rUTP	Mn2+	0.048 ± 0.002	634 ± 144	7.5 × 10−5	-	690
G	rCTP	Mg2+	0.86 ± 0.05	1427 ± 202	6.0 × 10−4	1	-
	rCTP	Mn2+	1.27 ± 0.04	4.9 ± 0.6	2.6 × 10−1	430	1
	rUTP	Mn2+	0.064 ± 0.004	995 ± 226	6.5 × 10−5	-	3970
C	rGTP	Mg2+	0.34 ± 0.06	6260 ± 1564	5.5 × 10−5	1	-
	rGTP	Mn2+	0.54 ± 0.02	7.9 ± 0.9	6.9 × 10−2	1260	1
	rUTP	Mn2+	0.030 ± 0.004	1274 ± 519	2.4 × 10−5	-	2950
A	rUTP	Mg2+	0.37 ± 0.04	4820 ± 860	7.6 × 10−5	1	-
	rUTP	Mn2+	0.89 ± 0.03	15 ± 2.0	5.9 × 10−2	780	-
TT dimer	rATP	Mg2+	0.54 ± 0.04	630 ± 124	8.3 × 10−4	1	-
	rATP	Mn2+	0.54 ± 0.02	3.6 ± 0.6	1.5 × 10−1	180	-
8-oxoG	rCTP	Mg2+	0.11 ± 0.01	590 ± 123	1.8 × 10−4	1	-
	rCTP	Mn2+	0.18 ± 0.01	4.0 ± 0.5	4.6 × 10−2	260	-

^a Relative efficiency was calculated using the following equation: f_rel = (k_cat/K_m)_Mn2+/(k_cat/K_m)_Mg2+. ^b 1/Relative efficiency was calculated using the following equation: f_rel⁻¹ = (k_cat/K_m)_correct/(k_cat/K_m)_incorrect. k_cat and K_m values were calculated using data from at least three independent experiments.