Cathepsin

Cathepsins are protease enzymes, categorized into multiple families. Cathepsins can be serine protease, cysteine protease, or aspartyl protease. There are about 15 classes of cathepsins in humans (Cathepsin A, B, C, D, E, F, G, H, K, L, O, S, V, W, and Z). Cathepsins are active in the low pH milieu of lysosomes and are versatile in their functions. Like other enzymes, they are vital for the normal physiological functions such as digestion, blood coagulation, bone resorption, ion channel activity, innate immunity, complement activation, apoptosis, vesicular trafficking, autophagy, angiogenesis, proliferation, and metastasis, among scores of others.

Numerous pathologies have been attributed to the dysregulated cathepsins, some of which include arthritis, periodontitis, pancreatitis, macular degeneration, muscular dystrophy, atherosclerosis, obesity, stroke, Alzheimer's disease, schizophrenia, tuberculosis, and Ebola.