Table 2.

Comparison of single-turnover parameters of LIG3β and LIG1

Single-turnover parameters were obtained at 150 mm ionic strength. All reactions contained 600 nm adenylylated enzyme and 100 nm nicked DNA substrate in the presence of 20 mm Mg²⁺ and the absence of ATP.

Kinetic parameter	LIG3β	LIG1a	Relative LIG1/LIG3β
kadenylylation (s−1)b	1.6 ± 0.2	1.3 ± 0.3	0.81
ktransfer (s−1)	0.89 ± 0.03	2.6 ± 0.6	2.9
kseal (s−1)	19 ± 6	12 ± 2	0.63
KMg, transfer (mm)	0.30 ± 0.07	0.15 ± 0.06	0.50
KMg, seal (mm)	18 ± 3	2.6 ± 0.9	0.14

^a LIG1 values were previously reported for Δ232 LIG1 under similar experimental conditions (34).

^b The microscopic rate constant for enzyme adenylylation was calculated using a k_cat value of 0.55 s⁻¹ with the net rate constants equation (Equation 4). The error is represented as S.D. from the mean (n ≥ 3).