... sorting in the Golgi, so that newly synthesized lysosomalenzymes appear in the medium. In the case of mutants, the appearance in the medium is thus an indicator that the enzyme has left the ... causeASA deficiency. In about half of the examined cases the mutant enzymes are retained in the ER [2,9,10], in the other half, enzymes can leave the ER and be degradedafter arrival in the lysosome ... rather uniform.Either the amino acid substitutions lead to an arrest of the mutant enzyme in the ER, or the enzyme is degra-ded in the lysosome after correct sorting [2,9–12]. Herewe have investigated...