TABLE 2

Specific activities of the purified NADH-dependent [FeFe]-hydrogenase Hyd1ABC

ReactionaHydrogenase activity (U · mg−1)b
H2 → MVox571
H2 → NAD+94.5
H2 → NAD+ + Fdox92.1c
H2 → NADP+<0.01
H2 → NADP+ + Fdox<0.01
H2 → Fdox<0.01
MVred → H224.3
NADH → H26.6
NADH + Fdred → H26.0
NADPH → H2<0.01
NADPH + Fdred → H2<0.01
Fdred → H2<0.01
  • a MVox, oxidized methyl viologen; FDox, oxidized ferredoxin; MVred, reduced methyl viologen; FDred, reduced ferredoxin.

  • b Activity was determined at 37°C, pH 7.5; 1 unit of activity (U) equals 2 μmol of electrons transferred per minute.

  • c Activity is the rate of NAD+ reduction at 340 nm in the presence of Fdox and not the rate of Fdox reduction (at 430 nm), which was not observed to occur.