TABLE 4

Kinetic parameters of PNP_Hyor

The K_m and k_cat values ± S.D. for the natural substrates of PNP_Hyor, for 2-chloro-2′-deoxyadenosine (cladribine) and 2-fluoroadenine-arabino-furanoside (fludarabine), and for P_i were determined using nonlinear regression analysis (using GraphPad Prism 5) from data obtained in at least two independent experiments.

	K_m	k_cat	k_cat /K_m
	µM	min⁻¹	(min ⋅ µM)⁻¹
Natural nucleoside substrates
Adenosine	61 ± 4	1099 ± 62	18
Inosine	283 ± 7	2757 ± 263	9.7
Guanosine	405 ± 135	1777 ± 419	4.4
Natural 2′-deoxynucleoside substrates
2′-Deoxyadenosine	47 ± 2	365 ± 1	7.8
2′-Deoxyinosine	2287 ± 455	1502 ± 213	0.7
2′-Deoxyguanosine	315 ± 46	832 ± 22	2.7
Nucleoside analogs
2-Chloro-2′-deoxyadenosine (cladribine)	80 ± 9	457 ± 59	5.7
2-Fluoroadenine-arabinofuranoside (fludarabine)	1120 ± 98	251 ± 131	0.2
Inorganic phosphate
Cosubstrate adenosine	672 ± 123	1134 ± 292	1.7
Cosubstrate inosine	978 ± 51	2793 ± 797	2.9
Cosubstrate guanosine	1252 ± 645	1101 ± 123	0.9
Cosubstrate 2′-deoxyadenosine	180 ± 10	487 ± 106	2.7
Cosubstrate 2′-deoxyguanosine	1573 ± 207	1209 ± 4	0.8