Compartmental distribution of β-hexosaminidase isoenzymes in I-cell fibroblasts

A characteristic of the huma lysosomal disorder I-cell disease is an abnormal excretion of most lysosomal hydrolases, including β-N-acetyl-D-glucosaminidase (EC 3.2.1.30; β-hexosaminidase) by cuyltured skin fibroblasts. Treatment of I-cell culture with cycloheximide or tunicamycin demonstrated that (1) I-cell fibroblasts rapidly excrete all newly synthesized β-hexosaminidase. (2) two qualitatively distinct pools of β-hexosaminidase isoenzymes exist inside I-cell fibroblasts, one of which is a rapid-turnover excretory pool, and (3) the induction of an abnormal glycosylation of β-hexosaminidase by tunicamycin in normal or I-cell fibroblast cultures does not affect subsequent excretion of the enzyme.