Background: Proteins of the matrix metalloproteinase (MMP) family are involved in the breakdown of extracellular matrix in normal physiological processes, such as embryonic development, reproduction, and tissue remodeling, as well as in disease processes, such as arthritis and metastasis. Most MMPs are secreted as inactive proproteins which are activated when cleaved by extracellular proteinases. However, MMP25 is a member of the membrane-type MMP (MT-MMP) subfamily, each member of this subfamily contains a potential transmembrane domain suggesting that these proteins are expressed at the cell surface rather than secreted. In addition, it is thought that this protein is activated intracellularly by furin-like enzymes. This protein activates MMP2 by cleavage. The gene has previously been referred to as MMP20 but has been renamed matrix metalloproteinase 25 (MMP25).