Table 2.

Specific activities of purified Fdh3 from Thermococcus onnurineus NA1.

Electron donors	Electron acceptors	Specific activity (U/mg)
Formate	MV 2+	241.7 $\pm$ 37.9
Formate	NAD +	11.2 $\pm$ 0.25
Formate	NADP +	77.4 $\pm$ 3.5
Formate	Fd 0317(ox)	0.830 $\pm$ 0.065
NADPH	BV 2+	108.6 $\pm$ 2.4
NADPH	CO2	1.00 $\pm$ 0.12
Fd 0317(red)	CO2	0.728 $\pm$ 0.094

One unit is equivalent to the transfer of 2 μmol of electrons per minute. Specific activity was calculated by spectrophotometric detection of the compounds marked in bold.