Table 2.

Sulfide:quinone reductase activity of SQR with sulfide as the substrate in the presence of different S⁰ acceptors. 100 nM SQR was reacted with 100 μM ubiquinone-1, 4 mM Cys or GSH and Na₂S ranging from 0 to 640 μM.

S0 acceptor	K m for sulfide (μM)	V max (μmol min −1 μmol −1)	k cat /K m (M−1 s−1)
Cys	72 ± 9	48 ± 2	(1.1 ± 0.1) × 104
GSH	38 ± 5	61 ± 2	(2.7 ± 0.4) × 104