Synthesis and processing of lysosomal enzymes of mouse kidney after treatment with [3H]fucose.

[3H]Fucose, intravenously injected into androgen-treated mice, was incorporated at high rates into the immunopurified kidney lysosomal enzymes beta-glucuronidase and beta-galactosidase. Initially, label was incorporated into high molecular weight proenzyme forms. Processing of fucose-labeled proenzyme forms to lower molecular weight mature forms was very rapid, being detectable at 30 min, and complete by 90 min, compared with the several hours required for processing of lysosomal enzymes labeled with amino acids. This result is consistent with addition of fucose residues within the Golgi apparatus just before transfer of lysosomal proenzyme forms to the lysosome where maturation is thought to occur. The combination of the high rates of incorporation of [3H]fucose and the known metabolic stability of this precursor sugar suggests that the mouse kidney system is advantageous for studies of the synthesis, processing, and degradation of fucose-containing complex oligosaccharides of lysosomal enzymes and, by extension, of other kidney glycoproteins.