Classification of Lysosomal Diseases

The lysosome plays an important role in many cellular processes, in addition to its catabolic and recycling function. A classification of lysosomal diseases based on the function of a defective protein in the lysosomal system focuses attention on understanding the pathogenetic mechanism and the development of potential forms of therapy. A genetic defect in the activity of a lysosomal catabolic enzyme leads to the progressive accumulation within the lysosome of partially digested substrates. Metabolites resulting from lysosomal catabolism are transported out of the lysosome by specific transporters in the lysosomal membrane. The neuronal ceroid lipofuscinoses, arises by diverse defects in the lysosomal system, are classified together because they share characteristic clinical and pathological features, particularly the accumulation of autofluorescent material within the lysosome. The cathepsins are a group of about 15 lysosomal proteases involved in the proteolysis and processing of a wide range of proteins in the endosomal/ lysosomal pathway.