TABLE 2.

Comparison of kinetic parameters for the sulfur transferase activities of rhodanese variants

Rhodanese	Donor	Acc	Km,Donor	Km,Acca	Vmaxb	kcat	n	kcat/Km,Donor	kcat/Km,Acc
			mm	mm	μmol min−1 mg−1	s−1		m−1 s−1	m−1 s−1
Wild-typec	GSSH	SO32−	0.450 ± 0.004	0.06 ± 0.01	609 ± 25	389		0.86 × 106	6.5 × 106
	S2O32−	Cys	0.35 ± 0.06	20.0 ± 0.5	13.0 ± 0.3	7.4	2.3 ± 0.1	21 × 103	0.37 × 103
	S2O32−	Hcy	0.3 ± 0.1	20.5 ± 1.9	15.5 ± 0.9	8.7	2.0 ± 0.1	29 × 103	0.4 × 103
	S2O32−	GSH	0.34 ± 0.05	21.0 ± 0.4	1.2 ± 0.02	0.67	2.3 ± 0.2	2.0 × 103	0.03 × 103
E102D	GSSH	SO32−	0.81 ± 0.07	0.17 ± 0.02	1302 ± 62	719		0.88 × 106	4.2 × 106
	S2O32−	Cys	0.50 ± 0.08	16.0 ± 0.7	11.3 ± 0.3	6.3	2.1 ± 0.1	13 × 103	0.4 × 103
	S2O32−	Hcy	0.46 ± 0.04	19 ± 1	13.1 ± 0.5	7.3	1.8 ± 0.1	16 × 103	0.4 × 103
	S2O32−	GSH	0.56 ± 0.06	18.0 ± 0.8	1.10 ± 0.03	0.61	2.1 ± 0.2	1.1 × 103	0.03 × 103
P285A	GSSH	SO32−	0.43 ± 0.04	0.28 ± 0.03	746 ± 35	412		0.96 × 106	1.5 × 106
	S2O32−	Cys	0.5 ± 0.2	19 ± 1	11.2 ± 0.4	6.2	1.9 ± 0.1	12 × 103	0.3 × 103
	S2O32−	Hcy	0.46 ± 0.03	20 ± 2	13.3 ± 0.9	7.4	2.2 ± 0.1	16 × 103	0.37 × 103
	S2O32−	GSH	0.52 ± 0.06	15.0 ± 0.8	0.93 ± 0.03	0.51	2.3 ± 0.2	1 × 103	0.03 × 103

^a K_m,Acc denotes the K_m for the sulfane sulfur acceptor.

^b V_max was estimated from data sets in which the acceptor concentration was varied. Hcy is homocysteine.

^c The values for wild-type rhodanese are from Ref. 11, and n is the Hill coefficient. S₂O₃²⁻ and SO₃²⁻ denote thiosulfate and sulfite, respectively.