TABLE 1.

Steady-state kinetic parameters for amino acid activation by SccytoPheRS

Data are the average of three replicates ± S.E.

Amino acid	kcat	Km	kcat/Km	Specificity (Phe/x)
	s−1	μm	s−1 × μm−1
Phe	58.2 ± 5.8	42.3 ± 7.0	1.4
o-Tyr	39.4 ± 0.9	310.7 ± 48.1	0.13	11
m-Tyr	26 ± 4a	1150 ± 230a	0.023a	71a
p-Tyr			0.014a	120a
l-DOPA			7.5 × 10−4 ± 4.4 × 10−5	1800

^a m-Tyr and p-Tyr values adapted from Bullwinkle et al. (10).