Properties of N-acetylglucosamine 1-phosphotransferase from human lymphoblasts.
Human lymphoblast and fibroblast cell lines from a patient with I-cell disease and normal individuals were characterized with respect to certain properties of UDP-N-acetylglucosamine:lysosomal enzyme precursor N-acetylglucosamine phosphotransferase. The enzyme isolated from normal lymphoblast and fibroblast cell lines expressed similar kinetic properties, substrate specificities and subcellular localizations. Coincident with the severe reduction of N-acetylglucosamine phosphotransferase activity in both I-cell fibroblast and lymphoblast cell lines, there was an increased secretion of several lysosomal enzymes compared to normal controls. Subsequent examination of N-acetyl-beta-D-hexosaminidase secreted by the I-cell lymphoblasts demonstrated a significant increase in adsorption of the I-cell enzyme to Ricinus communis agglutinin, a galactose-specific lectin. However, the I-cell lymphoblasts did not exhibit the significant decrease in intracellular lysosomal activities seen in I-cell fibroblasts. Our results suggest that lymphoblasts not only represent an excellent source for the purification of N-acetylglucosamine phosphotransferase, but in addition, represent a unique system for studying alternate mechanisms involved in the targeting of lysosomal enzymes.
Little
L
L
Department of Neurosciences, School of Medicine, University of California, San Diego, La Jolla 92093.
Alcouloumre
M
M
Drotar
A M
AM
Herman
S
S
Robertson
R
R
Yeh
R Y
RY
Miller
A L
AL
D002460:Cell Line; D002847:Chromatography, Agarose; D005347:Fibroblasts / Q000201:enzymology; D006801:Humans; D006867:Hydrolases / Q000378:metabolism; D007424:Intracellular Fluid / Q000201:enzymology; D007700:Kinetics; D008214:Lymphocytes / Q000201:enzymology*; D008247:Lysosomes / Q000201:enzymology; D008766:Methylmannosides / Q000378:metabolism; D009081:Mucolipidoses / Q000201:enzymology; D010766:Phosphorylation; D010770:Phosphotransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013347:Subcellular Fractions / Q000201:enzymology; D017855:Transferases (Other Substituted Phosphate Groups)
D008766:Methylmannosides; C008466:methylmannoside; D010770:Phosphotransferases; D017855:Transferases (Other Substituted Phosphate Groups); C030012:UDP-N-acetylglucosamine-lysosomal-enzyme-N-acetylglucosaminephosphotransferase; D006867:Hydrolases