REACTIONS OF H-2 WITH THE NICKEL SITE(S) OF THE [FENI] AND [FENISE] HYDROGENASES - WHAT DO THE MODEL COMPLEXES SUGGEST

In recent years, the structure(s) of the active site(s) of the nickel- containing hydrogenases (H(2)ases) and the mode of H-2 activation at t he nickel site(s) of these enzymes have been explored in detail, In su ch pursuit, spectroscopic and kinetic measurements have been performed on several H(2)ases. Despite all these data, the mechanism(s) of H-2 assimilation and H-2 evolution by the microorganisms remain rather elu sive at the present time. Several groups, including ours, have therefo re adopted the modeling approach to elucidate the structure and functi on of the biological nickel site. This review contains a concise accou nt of the spectroscopic experiments on the enzymes as a background for the subsequent modeling studies, It also provides a comprehensive sum mary of the modeling work by our group and others. Specific attempts h ave been made to correlate the spectral and reactivity parameters of g ood model complexes with those of the H(2)ases and derive conclusions regarding structural and functional characteristics of the biological nickel site.