Biosynthesis of alpha-N-acetylglucosaminidase in cultured human kidney carcinoma cells.

The biosynthesis of alpha-N-acetylglucosaminidase was studied in cultured human kidney carcinoma cells by labeling cells with 35S-methionine, isolation of the enzyme by immunoprecipitation and analysis on gel electrophoresis of the denatured polypeptide(s) and analysis of the native enzyme on linear sucrose gradient centrifugation. The enzyme is synthesized as precursor forms of apparent molecular weight 82,000-86,000. Processing of these precursors yields a polypeptide of apparent molecular weight of 80,000. The precursor-product relationship was indicated by pulse-chase as well as endocytosis experiments. Sucrose gradient centrifugation of the native enzyme shows that, extracellularly, the molecule is present with a molecular weight of 80,000; intracellularly, 80-90% of the enzyme is present with an apparent molecular weight of 240,000. We suggest that this is a polymeric form and that polymerization of alpha-N-acetylglucosaminidase is a late event of the maturation process.