Spectroscopic characterization of the key catalytic intermediate Ni-C in the O2-tolerant [NiFe] hydrogenase I from Aquifex aeolicus: evidence of a weakly bound hydride

Ni-C in the O-2-tolerant hydrogenase I from Aquifex aeolicus binds a hydride weaker than that in O-2-sensitive hydrogenases. This is in line with the enhanced light-sensitivity of Ni-C, greater lability of the hydride complex and increased catalytic redox potentials relevant to bio-H-2 oxidation.