Table 3.

Kinetic parameters for wild type Tgt and Tgt(Glu²³⁵Gln)

wild type Tgt	tRNATyr*	[3H]-guanine	preQ1	preQ0
KM [μM]	0.9 ± 0.2	1.2 ± 0.2	0.7 ± 0.2	0.9 ± 0.2
kcat [s−1] **	5.4 · 10−2	5.6 · 10−2	10.2 · 10−2	1.2 · 10−2
kcat/KM [μM−1s−1]	6.0 · 10−2	4.6 · 10−2	14.6 · 10−2	1.3 · 10−2
Tgt(Glu235Gln)	tRNATyr *	[3H]-guanine	preQ1	preQ0
KM [μM]	1.0 ± 0.1	3.3 ± 0.3	32 ± 7	< 0.5
kcat [s−1] **	7.0 ·10−2	7.6 ·10−2	10.0 ·10−2	0.6 ·10−2
kcat/KM [μM−1s−1]	7.0 ·10−2	2.4 ·10−2	0.3 ·10−2	> 1.2 ·10−2

^*using [3H]-guanine as 2nd substrate

^**taking into account the presence of Tgt as a homodimer able to bind and convert only one substrate tRNA molecule at a time.³⁴