Most of the hydrolytic enzymes of lysosomes function at
Acidic pH
Lysosomal enzymes are active at acidic pH (about 5), which is maintained within lysosomes. They are inactive at the neutral pH (about 7.2) characteristic of the rest of the cytoplasm.
Lysosomal enzymes function at acidic pH only, thus preventing uncontrolled digestion of cytoplasmic material.