Cathepsins mediate tumor metastasis

Table 1 Characters of human cathepsin familymembers

Cathepsin	Subtype	Endo/exopeptidase	Expressed tissue	Function
A	Serine	Exopeptidase	Platelets, primary human antigen presenting cell, testis and epididymis	Autophagy, elastic fiber formation, platelet activation
B	Cysteine	Exo and endo	Widely distributed in macrophages, hepatocytes	Protein catabolism, processing of antigens hormone activation and bone turnover
C	Cysteine	Exo	renal tubules, all endocrine organs Broadly distributed in tissues	Hydrolyze dipeptide esters,amides, anilides and beta-naphtylamides
D	Aspartic	Endo	Eccrine sweat, extracellular matrix and synovial fluid of cartilage	Protein degradation in an acidic milieu of lysosomes
E	Aspartic	Endo	Immune system	Antigen presentation
F	Cysteine	Endo	Antigen presenting cells	Antigen presenting
G	Serine	Endo	Polymorphonuclear leukocyte	Immune complex mediated inflammation production of angiotensin II, degradation of extracellular matrix
H	Cysteine	Endo	Ubiquitous in cells and tissues	Endopeptidase activity
L	Cysteine	Endo	Ubiquitously expressed	Keratinocyte differentiation, protein turnover, antigen presentation
K	Cysteine	Endo	Bone, ovary, heart, placenta, lung, skeletal muscle, colon and small intestine	Bone remodeling
O	Cysteine	Endo	Broadly distributed in tissues	Protein degradation and turnover
S	Cysteine	Endo	Spleen and professional antigen-presenting cells	Ii chain proteolysis
V	Cysteine	Endo	Thymus and testis, corneal epithelium	Production of enkephalin and neuropeptide Y
W	Cysteine	Endo	T-lymphocytes	Cell-mediated cytotoxicity
X	Cysteine	Endo	Immune system	Phagocytosis, regulation of immune responses
Z	Cysteine	Exo	Widely expressed in human tissues	Protein degradation