Table 2 The summary of kinetic properties of the WT PNP and the Y160W mutant vs. natural substrates and vs. 7-methylguanosine.

From: Single tryptophan Y160W mutant of homooligomeric E. coli purine nucleoside phosphorylase implies that dimers forming the hexamer are functionally not equivalent

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

  1. 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.
  2. *From 19, 250 μM m7Guo.
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