A cysteine protease involved in major histocompatibility complex class II antigen presentation and in intracellular and extracellular proteolysis.
Regulated by cystatin C, its endogenous inhibitor, at the cellular level.
Higher circulating levels associated with increased inflammation activity.
Increased activity may be involved in the development of cardiovascular disease by promoting and destabilizing atherosclerotic plaques.
Higher levels among elderly associated with increased mortality risk, and the relationship is stronger for women (Jobs E et al).