Table 3.

Substrate specifity of TthHPRT and TthAPRT.

Base	Conversion (24 h, %)a
	TthHPRT	TthAPRT
adenine	5.3	48.1
hypoxanthine	91.0	6.4
guanine	73.9	25.6
2-chloroadenine	0	52.9
2-fluoroadenine	0	31.1
6-mercapopurine	85.1	4.8
allopurinol	39.3	57.4
8-azaguanine	80.6	1.0
thymine	0	0
1,2,4-triazole-3-carboxamide	0	0
1,2,4-triazole-3-carboxy-N-methylamide	0	0

^aReaction mixtures (0.125 mL, 20 mM Tris-HCl, pH 8.0, 60 °C) contained 0.5 mM heterocyclic base, 0.5 mM PRPP, 0.5 mM MgCl₂, 5 mМ KH₂PO₄ and 0.4 μg of TthHPRT or TthAPRT.