Table 2.

Inhibition properties of some purines substituted at positions 2 and/or 6, and deoxyriboside of one of them, vs. H. pylori PNP.

Inhibitor	Kin [µM]	Kic [µM]	Kiu [µM]	alphaa
2,6-Dichloropurineb	22.2 ± 1.4	–	–	–
2,6-Dichloropurine	–	20.0 ± 4.9	23.5 ± 3.5	1.17 ± 0.44
6-Benzylthiopurineb	7.9 ± 0.4	–	–	–
6-Benzylthiopurine	–	7.5 ± 1.3	8.1 ± 0.7	1.07 ± 0.27
2-Chloro-6-benzyloxypurinec	–	18.3 ± 7.3	4.6 ± 0.5	0.25 ± 0.12
2-Chloro-6-benzyloxypurine	6.5 ± 0.4	–	–	–
2-Chloro-6-benzyloxypurine	–	–	3.8 ± 0.3	–
2-Chloro-6-benzylthiopurined	–	–	1.8 ± 0.2	–
2-Chloro-6-benzylthiopurine	–	13.2 ± 10.7	2.1 ± 0.3	0.16 ± 0.15
2-Chloro-6-benzylthiopurine-2′deoxy-9-ribofuranosidec	–	6.2 ± 2.4	2.9 ± 0.5	0.47 ± 0.24
2-Chloro-6-benzylthiopurine-2′deoxy-9-ribofuranosidec,e	–	12.6 ± 5.7	2.0 ± 0.2	0.16 ± 0.08

Data were obtained at 25 °C, in the 50 mM Hepes/NaOH buffer pH 7.0, at saturating phosphate concentration of 50 mM. If not otherwise indicated, m⁷Guo was used as variable substrate.

^aAlpha = K_iu/K_ic, see Equation (3) and (4) in Materials and methods.

^bNon-competitive inhibition model is the best.

^cMixed inhibition model is the best.

^dUncompetitive inhibition model and mixed type inhibition have similar probability. Due to poor solubility of the compound, data are limited to low inhibitor concentration, errors of K_ic and parameter alpha are big, so it is not possible to unequivocally decide which inhibition model is actually better, uncompetitive or mixed.

^eInhibition vs. guanosine as variable substrate.