Lysosomal cysteine proteinases and their significance in pathology

The lysosomal cysteine proteinases are synthesized in a form of pre-proenzymes. They are submitted to posttranslational glycosylation and phosphorylation. These modifications make possible transport the modified proteins into Golgi apparatus and into lysosomes. Some disturbances of transport which occur mainly in tumour cells result in an increase of these enzymes activities in cytosol and in intercellular compartment. The activity of cysteine proteinases is regulated by specific inhibitors (cystatin, kininogen) which exist in some tissues and body fluids. The evaluation of activity and concentration of proteinases and inhibitors is important in clinical diagnostics.