The invention relates generally to polypeptides that include a cleavable moiety that is a substrate for at least one matrix metalloprotease (MMP), to activatable antibodies and other larger molecules that include the cleavable moiety that is a substrate for at least one MMP protease, and to methods of making and using these polypeptides that include a cleavable moiety that is a substrate for at least one MMP protease in a variety of therapeutic, diagnostic and prophylactic indications.