Lysosomal cysteine proteases: more than scavengers

Lysosomal cysteine proteases were believed to be mainly involved in intrace llular protein degradation, Under special conditions they have been found o utside lysosomes resulting in pathological conditions. With the discovery o f a series of new cathepsins with restricted tissue distributions, it has b ecome evident that these enzymes must be involved in a range of specific ce llular tasks much broader than as simple housekeeping enzymes. It is theref ore timely to review and discuss the various physiological roles of mammali an lysosomal papain-like cysteine proteases as well as their mechanisms of action and the regulation of their activity. (C) 2000 Elsevier Science B.V. All rights reserved.