a phosphate monoester + H2O = an alcohol + phosphate The soluble form arises by proteolytic processing of the membrane-bound form. The membrane-bound form is converted to the soluble form by sequential proteolytic processing. First, the C-terminal cytoplasmic tail is removed. Cleavage by a lysosomal protease releases the soluble form in the lysosome lumen. N-glycosylated. The intermediates formed during enzymatic deglycosylation suggest that all eight predicted N-glycosylation sites are used. Lysosomal acid phosphatase has been shown to be deficient in cultured fibroblasts from patients manifesting intermittent vomiting, hypotonia, lethargy, opisthotonos, terminal bleeding and death in early infancy. Belongs to the histidine acid phosphatase family.