Matrix metalloproteinases (MMPs) and their substrates in myocardium. Collagenases (MMP-1, -8 and -13) have high substrate specificity for fibrillar collagens (e.g. collagen I, II and III) and extracellular matrix (ECM) proteins (proteoglycans, perlican, aggrecan, versican, etc.). Stromelysins (MMP-3 and -7) can digest ECM proteins and basement membrane proteins (e.g. collagen IV and fibronectin). Additionally, MMP-7 also degrades fibrillar collagens. The substrates for gelatinases (MMP-2 and -9) include gelatins, basement membrane proteins and ECM proteins. Membrane-type (MT-) MMPs breakdown basement membrane components, fibrillar collagens and ECM proteins.