Table 1.

Inhibition of Substrate Reduction by H₂

Additionsa	Specific Activity (nmol NH3 or C2H4/min/mg)b	Percent Inhibition of Maximal Activity
0.11 atm N2c	172 ± 15
0.11 atm N2, 0.89 atm H2	63 ± 4	63
4.6 μazodiformated	373 ± 36
4.6 μmol azodiformate, 1 atm H2	189 ± 7	58d
10 mM hydrazinee	540 ± 10
10 mM hydrazine, 1 atm H2c	530 ± 5	2
0.01 atm acetylenec	770 ± 16
0.01 atm acetylene, 1 atm H2	755 ± 17	2

^aGases are added as a partial pressure with argon added to achieve 1 atm total pressure.

^bAmmonia and ethylene were quantified as described in the Materials and Methods ection.

^cNitrogen and acetylene reduction assays were performed at pH 7.0 for 10 minutes using 100 μg of MoFe protein.

^dDiazene reduction assays were performed at pH 7.0 for 5 minutes using 200 μg of MoFe protein.

^eHydrazine reduction assays were performed at pH 7.2 for 10 minutes using 200 μg of the α-70^Ala MoFe protein.