TABLE 3.

Amino acid activation kinetic parameters of hmtLeuRS for Leu and its analogs

Discrimination factor represents the loss of catalytic efficiency relative to Leu.

Amino acids	Km	kcat	kcat/Km	Discrimination factor
	μm	s−1	s−1 m−1
Leu	30.4 ± 4.2	1.15 ± 0.25	37.8	1
Nva	6200 ± 130	1.31 ± 0.17	2.1 ×10−1	180
Val	19600 ± 900	0.62 ± 0.09	3.2 ×10−2	1180
ABA	16200 ± 1100	0.13 ± 0.02	8.0 ×10−3	4730
Met	20500 ± 1600	0.061 ± 0.008	3.0 × 10−3	12600