Table 1. Purification of recombinant DhsU1 of the LSSB.

	Total protein (mg)	Total activity (U)	Specific activity (U/mg)	Purification (fold)	Yield (%)
Crude extract	187.6	5.774	0.031	1.0	100
Ni-NTA	9.2	2.344	0.255	8.3	40.6

The reaction mixture contained 100 mM Tris-HCl (pH 8.0), 30 µM horse heart cytochrome c, 10 µM sodium sulfide and 25 µg crude or purified DhsU1. The total volume of the reaction mixture was 1.0 ml. The reaction was started by adding sodium sulfide. One unit of activity (U) is defined as 1 µmol of horse-heart cytochrome c reduced per minute.