Table 2.

The summary of kinetic properties of the WT PNP and the Y160W mutant vs. natural substrates and vs. 7-methylguanosine.

Kinetic parameter	WT	Y160W
Model	Allostery Eq. (2)	Allostery Eq. (2)
Phosphate as variable substrate, 0.4 mM m7Guo
Km [μM]	15 ± 4*	18.7 ± 2.7
Vmax [U/mg]	10.8 ± 0.7*	11.7 ± 0.4
a	267 ± 232*	390 ± 122
b	0.76 ± 0.06*	0.94 ± 0.05

Kinetic parameter	WT	Y160W
Model	Michaelis–Menten Eq. (1)	Michaelis–Menten Eq. (1)
Guo as variable substrate, 50 mM phosphate
Km [μM]	28 ± 4	128 ± 2
Vmax [U/mg]	51.1 ± 2.3	42.8 ± 0.3

Kinetic parameter	WT	Y160W
Model	Michaelis–Menten Eq. (1)	Michaelis–Menten Eq. (1)
m7Guo as variable substrate, 50 mM phosphate
Km [μM]	27.2*	71.3 ± 3
Vmax [U/mg]	22.7 ± 0.3	21 ± 1

Kinetic parameter	WT	Y160W
Model	Competitive inhibition Eq. (3)	Competitive inhibition Eq. (3)
Formycin A (m7Guo as variable substrate, 50 mM phosphate)
Ki [μM]	5.3 ± 0.4	42 ± 4

Data were obtained at pH 7.0, in 50 mM Hepes buffer, at 25 °C, with 50 mM phosphate using spectrophotometric methods described in “Methods” section. Parameters were obtained from the global fitting and are shown together with their standard deviations.

*From ¹⁹, 250 μM m⁷Guo.