Abstract
During the past decade, structures and functions of the active sites have been established for the nickel-based metalloenzymes present in the hydrogenases, ureases, carbon monoxide dehydrogenases/acetyl coenzyme A synthase, and methyl coenzyme M reductase. Roles of nickel in these Ni-containing enzymes serve as catalytic or redox centers. Model compounds and various biophysical techniques have been lent to elucidate aspects of the structure and function (catalytic mechanism) of the Ni sites in these enzymes. Structures/functions of these Ni-containing enzymes, biomimetic model compound studies, and the proposed catalytic mechanisms are presented.