1) Proteases which use a metal, normally zinc, in the catalytic mechanism. This group of enzymes is inactivated by metal chelators.

2) Encoded by metalloproteinase genes, metalloproteinases (endopeptidases) use a metal ion, normally zinc, in the catalytic process and preferentially cleave the Gln-Gly peptide bond. Metalloproteinases inactivated by metal chelators.