A quantitative immunoelectronmicroscopic study on soluble, membrane-associated and membrane-bound lysosomal enzymes...

We have used quantitative immunoelectronmicroscopy to compare the in situ localization of acid alpha-glucosidase, lysosomal acid phosphatase, beta-hexosaminidase and glucocerebrosidase in intestinal epithelial cells of the human duodenum. Differences between these four lysosomal enzymes were observed with respect to their presence at the apical cell surface. Transport to the apical membrane seems to be a more important intracellular route for lysosomal acid phosphatase and acid alpha-glucosidase than it is for beta-hexosaminidase. The membrane associated lysosomal enzyme glucocerebrosidase is not transported to the microvilli. The studies emphasize that lysosomal enzyme transport pathways are enzyme and cell type specific.