Protease inhibitors are biological or chemical compounds that function by reversibly or irreversibly binding to the protease. Many naturally occurring protease inhibitors are proteins. Protease inhibitors may be classified either by the type of protease they inhibit, or by their mechanism of action.
Metalloprotease inhibitors are cellular inhibitors of the Matrix metalloproteinases (MMPs). MMPs belong to a family of zinc-dependent neutral endopeptidases. These enzymes have the ability to break down connective tissue. Due to the role of MMPs in pathological conditions, inhibitors of MMPs may have therapeutic potential. MMP inhibitors can broadly be subdivided into non-synthetic (e.g. endogenous) or synthetic. Several potent MMP inhibitors have been identified, including hydroxymates, thiols, carbamoylphosphonates, hydroxyureas, hydrazines, β-lactams, squaric acids and nitrogenous ligands.
Serpins are a superfamily of proteins with similar structures that were first identified for their protease inhibition activity and are found in all kingdoms of life. The acronym serpin was originally coined because the first serpins to be identified act on chymotrypsin-like serine proteases (serine protease inhibitors). Protease inhibition by serpins controls an array of biological processes, including coagulation and inflammation, and consequently these proteins are the target of medical research. Serpin polymerisation not only reduces the amount of active inhibitor, but also leads to accumulation of the polymers, causing cell death and organ failure.