Peptidase family M54 (archaemetzincin or archaelysin) is a zinc-dependent aminopeptidase that contains the consensus zinc-binding sequence HEXXHXXGXXH/D and a conserved Met residue at the active site, and is thus classified as a metzincin. Archaemetzincins, first identified in archaea, are also found in bacteria and eukaryotes, including two human members, archaemetzincin-1 and -2 (AMZ1 and AMZ2). AMZ1 is mainly found in the liver and heart while AMZ2 is primarily expressed in testis and heart; both have been reported to be aminopeptidases, degrading synthetic substrates and peptides. The peptidase M54 family contains an extended metzincin concensus sequence of HEXXHXXGX3CX4CXMX17CXXC such that a second zinc ion is bound to four cysteines, thus resembling a zinc finger. Phylogenetic analysis of this family reveals a complex evolutionary process involving a series of lateral gene transfer, gene loss and genetic duplication events [, ].Archaemetzincin (from Mycococcus xanthus) seem to have evolved into a zinc-binding transcription factor fulfilling only a structuralrole [, ]. The structure of archaemetzincin from Methanopyrus kandleri has been resolved [].
