TABLE 2.

Electron acceptor specificity of hydrogenase^a

Electron acceptor (concn)	Eo′ (mV)c	Relative activity (%)
		H. pylori	H. hepaticus
Methylene blue (200 μM)	11	100	100
Phenazine methosulfate (400 μM)	80	>100	89
DCPIPb (200 μM)	217	54	68
Ferricyanide (1 mM)	360	85	68
Cytochrome c (100 μM)	250	33	71
Benzyl viologen (1 mM)	−360	<0.5	<1.0

^aThe 100% activities (methylene blue rate) were 382 and 62 nmol/min/mg of protein for H. pylori (membranes) and H. hepaticus (permeabilized cells), respectively. The H. pylori data are from reference 12. The H. hepaticus permeabilized cells were prepared as described in footnote a of Table 1, and protein was measured with bicinchoninic acid (Pierce Chemical Co) after adding 1% sodium dodecyl sulfate and then heating cells (90°C for 10 min). All electron acceptor activities were determined at saturating levels anaerobically in the presence of 50 μM sodium dithionite.

^bDCPIP, 2, 6-dichlorophenolindophenol.

^cEo′, standard oxidation-reduction potential.