At the end of this cascade, a group of enzymes called Matrix Metallo Proteinases (MMP’s) are released. What Are MMP’s (Matrix Metallo Proteinases)? Matrix Metallo Proteinases (MMP’s) are enzymes that break down tissue. After an injury or ‘insult’ to skin, the body’s natural response is to destroy the injured tissue and create new tissue. MMP’s are needed for remodeling skin in wound healing. This make sense if there is a real wound, such as a cut from a knife.