The sorting of lysosomal enzymes in 
a normal cell is shown on the left. 
First, enzymes receive a chemical 
"address label" in the Golgi 
apparatus (a), and move in vesicles 
(b) to a lysosome (c). Any enzyme 
that is accidentally swept out of the 
cell (d) is recaptured and taken 
back to the lysosome (e). If some 
part of this process goes awry, a 
lysosomal storage disorder can 
result. For example, in Hurler's 
syndrome (center), an enzyme is not 
produced (f), and the lysosome 
therefore lacks that enzyme (g). If 
correctly tagged enzyme is added to 
the cells in test tubes (h), the cells can 
capture the enzyme and take it to the 
lysosome (i). In l-cell disease (right), 
enzymes are correctly made, but they 
are not tagged in the Golgi (j), and 
therefore are not sent to the lysosome. 
When such enzymes leave the cell 
(k), they cannot be recaptured (I) and 
so the lysosome remains empty (m). 
Normal cell 
Hurler's syndrome 
l-cell disease 
35 
