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 MMP's are secreted as inactive proproteins which are activated when cleaved by extracellular proteinases. The protein encoded by this gene is considered a member of the membrane-type MMP (MT-MMP) subfamily. However, this protein is unique among the MT-MMP's in that it is a GPI-anchored protein rather than a transmembrane protein. The protein activates MMP-2 by cleavage.?