Cystatin-B belongs to the cystatin protein superfamily. It is an intracellular thiol proteinase inhibitor that binds papain, and cathepsins L, H, and B. Cystatin-B may play a role in cell protection from proteases that leak from lysosomes. Cystatin-B is widely distributed in many tissue and cell types. Genetic defects cause progressive myoclonic epilepsy type 1. Elevated levels of cystatin-B have been found in epithelial tissue of ovarian cancer patients.
Swiss-Prot Accession Number: P04080