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Cathepsin B from human liver has been used:

• as a positive control in the screening Cathepsin B inhibitor assay
• in wall extension (expansin activity) assay
• in microinjection human foreskin fibroblasts to test its effect on apoptosis induction

Cathepsin B is a lysosomal cysteine proteinase which hydrolyzes proteins with a broad specificity for peptide bonds. Cathepsin B may be a useful tool in Alzheimer′s research, as it may have a role in the natural defense against the disease . Cathepsin B may be used to cleave procaspase 1 and procaspase 11, and to induce apoptosis in digitonin-permeabilized cells.

Cathepsin B gene is mapped to human chromosome 8p23.1. It is a lysosomal cysteine with 252 amino acids distributed in two chains and is homologous to rat liver sequence. It has disc shaped structure with two domains namely the left-hand ′L′ domain at the amino terminal and right hand ′R′ domain at the carboxyl-terminal.

Cathepsin B displays an endopeptidase and peptidyl dipeptidase activities. It may be associated with the pathophysiology of tumors. Cathepsin B is also regarded as a prominent protease in Leishmaniasis. It is overactivated in muscular dystrophy, pulmonary emphysema, and bone resorption.

Cathepsin B is purified by affinity chromatography on the semicarbazone of Gly-Phe-glycinal-linked to Sepharose 4B, with elution by 2,2'-dipyridyl disulfide [Rich et al. Biochem J 235 731 1986, Methods Enzymol 80 551 1981].