High Quality Content by WIKIPEDIA articles! Matrix metalloproteinases (MMPs) are zinc endopeptidases, commonly called metzincins. MMP enzymes represent an ancient family of proteins with major similarities in genetic make-up that are present in a range of diverse organisms from unicellular bacteria to multicellular vertebrates and invertebrates. The superfamily is distinguished due to its motif consisting of three histidines bonded to zinc at the catalytic site. The metzincins are divided into four smaller families: seralysins, astacins, adamalysins (ADAMs), and MMPs. The MMP family is formed by twenty related zinc-dependent enzymes. They are noted for having the ability to degrade extracellular matrix proteins, such as collagens, laminin, and proteoglycans. These calcium- and zinc-dependent proteases are activated at neutral pH and twenty-three have been found present in mammalian cells. Plant MMPs show structural similarity to MMPs found in mammals, such as the presence of an auto-regulatory cysteine switch domain and a zinc-binding catalytic domain.