LYSOSOMAL-ENZYME TARGETING: THE PHOSPHORYLATION OF SYNTHETIC D-MANNOSYL SACCHARIDES BY UDP-N-ACETYLGLUCOSAMINE:LYSOSOMAL-ENZYME N-ACETYLGLUCOSAMINE-PHOSPHOTRANSFERASE FROM RAT-LIVER MICROSOMES AND FIBROBLASTS

Article abstract of DOI:10.1016/S0008-6215(00)90298-2

Phosphorylation of the D-mannose residues of lysosomal-enzymes is essential for the uptake and intracellular transport of these enzymes to lysosomes.The GlcNAc-P-transferase which is involved in the phosphorylation reaction seems to recognize a signal, probably a protein conformation, common to many lysosomal enzymes.To evaluate the role of the carbohydrate portion of the enzyme in these phosphorylation reactions, the acceptor specificity of GlcNAc-P-transferase from rat-liver microsomes and fibroblasts was examined with the aid of synthetic D-mannosyl disaccharides and derivatives that are closely related to the high-mannose type of oligosaccharides.Four methyl D-mannobiosides were synthesized, and their structures were established by 13C-n.m.r. spectroscopy.Of all the D-mannosyl saccharides tested, α-D-Man-(1->2)-α-D-Man-(1->OMe) was found to be the best acceptor, thereby suggesting that oligosaccharide structure may also have a role to play in recognition by this enzyme.