Interaction of arylsulfatase A with UDP-N-acetylglucosamine : lysosomal enzyme-N-acetylglucosamine-1-phosphotransferase

The critical step in lysosomal targeting of soluble lysosomal enzymes is th e recognition by an UDP-N-acetyl-glucosamine:lysosomal enzyme-N-acetylgluco samine-1-phosphotransferase. The structure of the determinant common to all lysosomal enzymes for proper recognition by the phosphotransferase is not completely understood. Our current knowledge is largely based on the introd uction of targeted amino acid substitutions into lysosomal enzymes and anal ysis of their effects on phosphotransferase recognition. We have investigat ed the effect of eight anti-arylsulfatase A monoclonal antibodies on the in teraction of arylsulfatase A with the lysosomal enzyme phosphotransferase i n vitro, We also show that a lysine-rich surface area of arylsulfatases A a nd B is essential for proper recognition by the phosphotransferase, Monoclo nal antibodies bind to at least six different epitopes at different locatio ns on the surface of arylsulfatase A. All antibodies bind outside the lysin e-rich recognition area, but nevertheless Fab fragments of these antibodies prevent interaction of arylsulfatase A with the phosphotransferase, Our da ta support a model in which binding of arylsulfatase A to the phosphotransf erase is not restricted to a limited surface area but involves the simultan eous recognition of large parts of arylsulfatase A.