TABLE 1.

Kinetic parameters for aminoacylation of tRNA^Val by wild-type and mutant ValRS

ValRS variant	Km	kcat	kcat/Km	Relative efficiency
	μm	s–1	m–1 s–1
Wild-type	0.2 ± 0.02a	0.2 ± 0.04	1 × 106	1
Δ32–71	10 ± 0.08	0.06 ± 0.02	6 × 103	0.006
Δ1–97	NDb	ND	ND	ND

^aEach value is determined from a hyperbolic fit of two independent data sets

^bND, not determined