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. Author manuscript; available in PMC: 2008 Sep 12.
Published in final edited form as: Biochemistry. 2006 Jan 17;45(2):617–625. doi: 10.1021/bi051863d

Table 2.

Experimental Conditions for Hypoxanthine and Xanthine Kinetics Determinations.

enzyme [Hypoxanthine] μM [Xanthine] μM Time Courses (both substrates)
htTGT(wt) 25–3000 10–1500 120 min
htTGT(D143A) 50–2000 1–750 120 min
htTGT(D143N) 50–2000 0.5–750 120 min
htTGT(D143S) 1–3000 1–3000 4 hr
htTGT(D143T) 1–3000 1–3000 4 hr

[tRNA] = 20 μM for all enzymes and [TGT] = 100 nM for all except htTGT(D143S) & htTGT(D143T) = 250 nM. Assays were conducted in 100 mM HEPES (pH 7.3), 20 mM MgCl2 and 5 mM DTT at 37 °C as described in Methods.