title: Heterogeneity of N-acetylglucosamine 1-phosphotransferase within mucolipidosis III.
abstract: The primary defect responsible for mucolipidosis III is a deficiency of UDP-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine 1-phosphotransferase activity (GlcNAc phosphotransferase). Genetic complementation analysis of cultured fibroblasts derived from 12 patients with mucolipidosis III identified complementation groups A, B, and C (Honey, N. K., Mueller, O. T., Little, L. E., Miller, A. L., and Shows, T. B. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 7420-7424). The GlcNAc phosphotransferase activity present in the cell lines comprising the complementation groups was characterized with respect to endogenous substrates and two exogenous acceptors, alpha-methyl-D-mannoside and high mannose glycopeptides. All group C cell lines and one group A cell line were found to have normal GlcNAc phosphotransferase activity levels at 37 degrees C when screened with these exogenous acceptors. The enzyme activity in group A cell lines was within normal range when assayed at 23 degrees C. Inhibition of the phosphorylation of alpha-methyl-D-mannoside in the presence of increasing amounts of endogenous substrate N-acetyl-beta-D-hexosaminidase B was demonstrated in normal cell lines at 23 and 37 degrees C and in group A cells at 23 degrees C. However, group C cell lines did not show any inhibition at either temperature. This suggests that the alteration of the GlcNAc phosphotransferase from individuals in group C affects the recognition site for the protein portion of lysosomal enzymes, whereas group A individuals have mutations which result in a temperature-sensitive enzyme.
mesh_terms: D002460:Cell Line; D005816:Genetic Complementation Test; D006596:Hexosaminidases / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008766:Methylmannosides / Q000378:metabolism; D009081:Mucolipidoses / Q000201:enzymology*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D010920:Placenta / Q000201:enzymology; D013395:Sucrose / Q000494:pharmacology; D013696:Temperature; D017855:Transferases (Other Substituted Phosphate Groups); D001619:beta-N-Acetylhexosaminidases
chemical_list: D008766:Methylmannosides; C008466:methylmannoside; D013395:Sucrose; D010770:Phosphotransferases; D017855:Transferases (Other Substituted Phosphate Groups); C023222:UDPacetylglucosamine-dolichyl-phosphate acetylglucosamine-1-phosphate transferase; D006596:Hexosaminidases; D001619:beta-N-Acetylhexosaminidases