The active site and catalytic mechanism of NiFe hydrogenases

Abstract

This Perspective describes, from our own personal experiences, how the architecture of the NiFe hydrogenase active site has been elucidated by a combination of protein crystallography, Electron paramagnetic resonance and Fourier transform infrared spectroscopic studies. Thus within a period of eight years our perception of the active center has changed from a mononuclear Ni center with S and N/O coordination to a binuclear NiFe unit with thiolate (to Ni and Fe) and CO and CN⁻ (to Fe) ligands. This biologically unusual organometallic cluster poses a real challenge in terms of understanding the role of its different components. Current ideas concerning the NiFe hydrogenase catalytic mechanism are discussed in this context.