The family consists of papain and related plant proteases such as chymopapain (chymopapain), bromelain (bromelain), ficin (ficin), kiwi hormone (actinidin), etc., cruzipain and related parasites proteases, and lysosomal cathepsin. Most of cathepsin cysteine proteases belong to the class of papain, a few belong to aspartic protease (CTSD, CTSE) and serine proteases (CTSA, CTSG, CTSR). Based on amino acid sequence homology, CTSL lysosomal cathepsins can be divided into categories (including CTSL, CTSV, CTSK, CTSS, CTSH) and CTSB (including, E-64 CTSB, and proteins similar thereto). CTSL class cathepsin precursor peptide region has conserved motif (motif) "ER / WFNIN", while CTSB class not have this structure. Between CTSF and CTSW has both highly conserved molecular structure and chromosomal localization, and the precursor peptide has "ERFNAQ" motif, so they called Wex and other recommendations CTSF protease, but it was also classified CTSL their class . CTSC, CTSO and CTSX current classification is not yet clear. Rief other study found that CTSO protein folding configuration and CTSL very similar. Synthesis and processing of cathepsin hydrolysis by cathepsin inactive zymogen precursor (preproenzyme) formed. Usually first ribosome binding form a precursor film of a synthetic zymogen, after entering the endoplasmic reticulum, glycosylated modified, then the zymogen (proenzyme) form into the Golgi apparatus, the occurrence of further phosphorylation to form 6-phosphate mannose (M6P), and finally by M6P specific receptor (M6PR) identifying the role of the lysosomes, transported to the lysosomes.