Cathepsin B Novocastra
Cathepsin B is one member of a family of proteolytic enzymes and is expressed in cytoplasmic lysosomes in different types of normal and neoplastic tissues. It is a cysteine protease and like most cathepsins is involved in cellular metabolism such as protein degradation. Immunohistochemical studies have detected expression in bowel mucosa, skin, prostate and thyroid. Staining for cathepsin B, in common with other cathepsins, may be so intense that it appears to be nuclear in some cells. A proportion of endothelial cells are positive in many tissues. This has been reported previously where it has been described as sprouting endothelial cells.