Table 2.

Kinetic parameters for AtSrx and its variants for Prx and ATP

Enzyme	Substrate	kcat/KM (M−1 s−1)
AtSrx WT	2-Cys Prx-SO2H	1.39×102
	ATP	0.14×102
R28Q AtSrx	2-Cys Prx-SO2H	0.27×102
	ATP	0.03×102
K40Q AtSrx	2-Cys Prx-SO2H	0.47×102
	ATP	0.02×102
E76A AtSrx	2-Cys Prx-SO2H	1.46×102
	ATP	0.16×102

Data were determined by measuring P_i at 5 min in reactions containing 30 μM AtSrx, 1 mM Mg, 0–40 μM Prx-SO₂H or 0–500 μM ATP in 50 mM TRIS-HCl (pH 7.5).