Table 1.

Kinetic parameters of CD and thiosulfate sulfurtransferase activities of CD–Rhd and its C466S variant

Donor	Reductant	KM (μM)	kcat (s−1)	kcat/KM (M−1 s−1)
CD–Rhd
l-cysteine	DTT	310 ± 38	6.8 ± 0.5	2.2 ± 0.2 × 104
l-cysteine	GSH	476 ± 146	8.2 ± 1.2	1.8 ± 0.2 × 104
l-cysteine	β-ME	273 ± 26	6.1 ± 0.2	2.2 ± 0.1 × 104
Thiosulfate	β-ME	756 ± 51	2.0 ± 0.1	2.7 ± 0.3 × 103
CD–Rhd C466S
l-cysteine	DTT	31 ± 5	1.01 ± 0.01	3.3 ± 0.6 × 104
l-cysteine	GSH	597 ± 168	0.93 ± 0.12	1.6 ± 0.2 × 103
l-cysteine	β-ME	346 ± 79	0.53 ± 0.03	1.6 ± 0.3 × 103
Thiosulfate	β-ME	ND	ND	ND

The apparent K_M and turnover values (k_cat) were calculated by nonlinear regression using the Michaelis–Menten equation. The data are represented as mean ± SD of three independent experiments.

Abbreviation: ND, not detected.