Keratan sulfate degradation is carried out sequentially in the lysosome where two enzymes are involved in the removal of beta-galactoside moieties: N-acetylgalactosamine-6-sulfatase (GALNS, deficient in MPS IVA) and β-galactosidase (GLB1, impaired in Morquio Type B disease, MPS IVB). The gene discussed is GLB1; the disease is mucopolysaccharidosis type 4A.