From the PrefaceAlthough it has been suspected since ancient times that metals participate in biological processes, details of the manner in which they might exert a function have until recently remained unknown. It is now appreciated that metals play roles in catalysis, hormone action, gene and other regulatory functions, structural stabilization of macromolecules, muscle contraction, nerve conduction, and transport. Metallobiochemistry is a field which has grown and matured rapidly over the past decade. Metalloenzymes have been the central investigating targets. This volume provides both the emerging and practicing metallobiochemist with the necessary tools to answer what should be the number one and two questions: Is this enzyme a metalloenzyme? What metal is it?