The kinetic constants of MBP-NucPNP for MTA and adenosine^a.

Substrate	k cat (s−1)	K m (μM)	k cat/Km (μM−1 s−1)
MTA	0.15 ± 0.01	43.5 ± 4.1	3.4 × 10−3
Adenosine	0.49 ± 0.02	90.3 ± 8.2	5.5 × 10−3

^aThe k_cat, K_m, and k_cat/K_m were determined at a fixed concentration of 10 mM phosphate with varied MTA or adenosine catalyzed by 1 μM of MBP-NucPNP.