 Although primarily a lysosomal enzyme, ARSB was also found to localize at the cell membrane of hepatocytes, sinusoidal endothelial cells, and Kupffer cells in the liver, as well as in the apical membranes of normal and malignant colonic and prostatic epithelial cells, by immunohistochemistry and immunofluorescence studies.Membrane immunostaining in the colon and prostate was lower in malignant than in normal tissue and also was lower in higher grade malignancies.ARSB activity assay in the membrane and cytosol fractions of cultured bronchial epithelial cells showed that the activity was several-fold greater in the membrane fraction.