Light and heavy lysosomes: characterization of N-acetyl-beta-D-hexosaminidase isolated from normal and I-cell disease lymphoblasts.
We previously reported that I-cell disease lymphoblasts maintain normal or near-normal intracellular levels of lysosomal enzymes, even though N-acetylglucosamine-1-phosphotransferase activity is severely depressed or absent (Little et al., Biochem. J., 248, 151-159, 1987). The present study, employing subcellular fractionation on colloidal silica gradients, indicates that both light and heavy lysosomes isolated from I-cell disease and pseudo-Hurler polydystrophy lymphoblasts possess normal specific activity levels of N-acetyl-beta-D-hexosaminidase, alpha-D-mannosidase and beta-D-glucuronidase. These current findings are in contrast to those of cultured fibroblasts from the same patients, where decreased intralysosomal enzyme activities are found. Column chromatography on Ricinus communis revealed that N-acetyl-beta-D-hexosaminidase in both heavy and light I-cell disease lysosomal fractions from lymphoblasts possesses an increased number of accessible galactose residues (30-50%) as compared to the enzyme from the corresponding normal controls. Endo-beta-N-acetylglucosaminidase H treatment of N-acetyl-beta-D-hexosaminidase from the I-cell lysosomal fractions suggests that the majority of newly synthesized high-mannose-type oligosaccharide chains are modified to complex-type carbohydrates prior to being transported to lysosomes. This result from lymphoblasts differs from previous findings with fibroblasts, where N-acetyl-beta-D-hexosaminidase from I-cell disease and pseudo-Hurler polydystrophy lysosomes exhibited properties associated with predominantly high-mannose-type oligosaccharide chains.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Neurosciences, University of California, San Diego School of Medicine, La Jolla 92093.
A L
AL
Miller
V
V
Norton
R
R
Robertson
M
M
Jenks
R Y
RY
Yeh
D
D
Wright
D000328:Adult; D002458:Cell Fractionation; D002478:Cells, Cultured; D002648:Child; D002846:Chromatography, Affinity; D004721:Endoplasmic Reticulum / Q000201:enzymology; D006026:Glycoside Hydrolases / Q000032:analysis; D006412:Hematopoietic Stem Cells / Q000201:enzymology; D006596:Hexosaminidases / Q000378:metabolism; D006801:Humans; D037102:Lectins / Q000378:metabolism; D008214:Lymphocytes / Q000201:enzymology*; D008247:Lysosomes / Q000201:enzymology*; D009081:Mucolipidoses / Q000201:enzymology*; D009439:Neuraminidase / Q000378:metabolism; D037121:Plant Lectins; D001619:beta-N-Acetylhexosaminidases / Q000302:isolation & purification*
D037102:Lectins; D037121:Plant Lectins; C017707:Ricinus communis agglutinin-1; D006026:Glycoside Hydrolases; D006596:Hexosaminidases; D009439:Neuraminidase; D001619:beta-N-Acetylhexosaminidases