Table 2. Substrate specificity of MTH1.

Substrate	Km (µM)	kcat (s–1)a	kcat/Km (s–1µM–1)
2-OH-rATP	4.3	4.7	1.09
8-OH-rGTP	55	2.6	0.05
8-OH-rATP	51	1.1	0.02
2-OH-dATPb	8.3	13.9	1.68
8-OH-dGTPb	15.2	12.3	0.81
8-OH-dATPb	13.9	10.8	0.78
dGTPb	258	15.7	0.06

The reaction mixtures, containing 1–20 µM of substrate were incubated with 1 nM MTH1 (for 2-OH-rATP) or 20 nM MTH1 (for 8-OH-rGTP and 8-OH-rATP) for 5 min at 30°C.

^aThe k_cat value was calculated as molecules of product formed per molecule of MTH1 per second.

^bThese values are from Fujikawa et al. (12).