Table 2.

Kinetic properties of wild-type CSE (WT) and the indicated mutants using cystine as substrate. CSE β-lyase reactions were examined for the Cys-SSH level with a sulfane sulfur-specific fluorescent probe, SSP4, as described in the Materials and Methods section. Values represent the mean ± S.E. for three independent experiments. Km and Vmax values were determined from double-reciprocal plots (Lineweaver-Burk) of data obtained from experiments performed with three or four concentrations (0.05–1 mM) of cystine.

CSE	WT	C136V	C171V	C136V/C171V
Km (mM)	0.271 ± 0.026	0.554 ± 0.046	0.308 ± 0.029	0.32 ± 0.024
Vmax (Fluorescence Intensity)	57.79 ± 3.61	193.92 ± 14.31	78.10 ± 5.96	180.64 ± 7.94
Vmax/Km	213.35	349.91	253.78	563.76