Table 1.

Comparison of substrate activity of TvPNP and EcPNP

Substrate	TvPNP	EcPNP
	nmoles/mg-h
Adenosine	501,000	398,000
9-β-D-arabinofuranosyl adenine	38,000	620
2-F-adenosine	185,000	215,000
2-F-2′-deoxyadenosine (F-dAdo)	400,000	435,000
9-β-D-arabinofuranosyl-2-F-adenine (F-araA, fludarabine)	32,000	1,300
2-Cl-2′-deoxyadenosine (cladribine)	350,000	39,000
Inosine	154,000	342,000
2′-deoxyinosine	660,000	664,000
9-β-D-arabinofuranosyl-hypoxanthine	48	61
Guanosine	14,000	156,000
9-β-D-arabinofuranosyl-guanine	16	310
9-β-D-ribofuranosyl-6-methylpurine	155,000	92,000
9-[2-deoxy-β-D-ribofuranosyl]-6-methylpurine (MeP-dR)	484,000	461,000
9-β-D-arabinofuranosyl-6-methylpurine	570	14

Enzymes were incubated with 100 μM of each compound and cleavage rate determined using reverse phase HPLC to separate base from nucleoside. The results with EcPNP have been reported previously [23] except for guanosine, 9-β-D-arabinofuranosyl-guanine, and 9-β-D-arabinofuranosyl-6-methylpurine. Each value is the mean of at least two determinations which exhibited good agreement.