The cathepsin family of proteolytic enzymes contains several diverse classes of proteases. The cysteine protease class comprises cathepsins B, L, H, K, S, and O. The aspartyl protease class is composed of cathepsins D and E. Cathepsin G is in the serine protease class. Most cathepsins are lysosomal and each is involved in various cellular events such as peptide biosynthesis and protein degradation. The propeptide region of cathepsin H is highly homologous to other cathepsins. This region is