Re: lysosomes

Lysosomal diseases result from deficiency of one of the many enzymes involved
in the normal, step-wise breakdown of macromolecules.  Some of the causes of
lysosomal storage diseases are: a) a deficiency of a lysosomal enzyme or sub-
unit thereof, b) the deficiency of a protein assisting one or more lysosomal
enzymes in their catalytic function by activation and/or stabilization, or by
substrate presentation, c) the deficiency or dysfunction of a lysosomal membrane
carrier protein essential for the export of degradation products from the 
lysosomal interior to the cytoplasm, or d) defective targeting of lysosomal
proteins to the lysosomes.  Studies in vitro have shown that cells from
enzyme-deficient patients can be corrected by addition of the missing enzyme.  
Advances in gene therapy are likely to improve the successful treatment of
lysosomal disorders by facilitating the large scale production of clinically
effective proteins and also by enabling the stable and safe introduction of 
normal lysosomal genes  into cells of affected patients.