ABSTRACT
Zinc is present in and essential to all forms of life. In higher mammals zinc is second in abundance only to iron among the trace metals. Zinc is essential for the catalytic function and/or structural stability of more than 300 distinct enzymes, which participate in biological reactions encompassing the synthesis and degradation of all the major metabolites. In addition, in numerous other proteins, such as transcription factors, zinc plays an essential structural and/or functional role. Zinc chemically combines in the + 2 oxidation state being neither oxidised nor reduced in biological reactions. Within enzymes the zinc can have either a catalytic, structural or regulatory role. The zinc metalloproteases are a growing subset of such enzymes whose catalytic functions are critically dependent on the zinc ion at the active site. This group of enzymes can be subdivided into distinct families on the basis of both sequence and structural information. Although the HEXXH consensus sequence is the most common zinc binding motif in the zinc metalloproteases, several other metal binding motifs exist and undoubtedly others remain to be elucidated. This chapter provides a brief overview of the biological importance of zinc and its catalytic properties, and then sets out a framework for the grouping of the known zinc metalloproteases (most of which are discussed in later chapters in this volume) into families on the basis of sequence and structural similarities around the zinc binding site.
