Table 2.

Kinetic constants of AlaRSTT in amino acid activation reaction

Amino acid	k cat (s–1)	K m (mM)	k cat /Km (mM–1 s–1)	Discrimination factor
l-Alaa	7.88 ± 2.6	0.139 ± 0.012	56	1
d-Alab	0.21 ± 0.03	2.19 ± 0.50	0.12	467
Glyc	6.5 ± 1.6	22 ± 8	0.29	193
l-Serd	2.3 ± 0.8	10 ± 2	0.236	237
d-Sere	0.127 ± 0,028	407 ± 59	0.00031	180 645

The data shown represent mean values ± SEM (n = 3), measured by ATP-PPi exchange assay at 60 °C (pH 7.5).

^a/cAlaRSTT was assayed at 15 nM concentration.

^bAlaRSTT was assayed at 1 μM concentration.

^dAlaRSTT was assayed at 100 nM concentration.

^eAlaRSTT was assayed at 2.5 μM concentration.