Cathepsins are papain family cysteine proteinases that represent a major component of the lysosomal proteolytic system.
Members
| CTSA | CTSB | CTSC | CTSD | CTSE | CTSF | CTSG | CTSH | CTSI | CTSJ |
| CTSK | CTSL | CTSM | CTSN | CTSO | CTSP | CTSQ | CTSR | CTSS | CTST |
| CTSU | CTSV | CTSW | CTSY | CTSZ |