Abstract
Mammalian liver possesses sites, not shared by other organs, which bind several glycoproteins whose terminal sugars are galactose. Such proteins are taken up rapidly—and almost exclusively—by the liver following intravenous administration (Morell, et al. J. Biol. Chem. 246:1461, 1971). We determined whether the coupling of p-antinophenyl-thio- derivatives of either galactose or glucose to purified Aspergillus amylase could increase binding of the enzyme to liver in vitro and in vivo. The enzymes to which sugar was coupled (gal-amylase or glu-amylase) had 60% of the enzyme activity of the unmodified amylase. Employing the assay of Van Lenten and Ashwell (J. Biol. Chem. 247:4633, 1972) the greatest affinity for the binding site on liver cell membrane was observed with gal-amylase; over 50 times as much glu-amylase was required for comparable binding. Unmodified amylase did not bind even when 105 times as much was used. Mice were injected intravenously with either unmodified 125I-amylase, 125I-gal-amylase or 125I-glu-amylase and sacrificed 5-15 minutes later. The proportion of radioactivity found in whole liver was highest for gal-amylase, intermediate for glu-amylase and least for unmodified amylase. It remains to be determined whether the rapid uptake of gal-amylase is associated with diminished immune response and to what extent its enzyme activity persists in the liver.
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Holtzman, N., Bell, G., Krantz, M. et al. ENZYME REPLACEMENT THERAPY: DIRECTING EXOGENOUS ENZYME TO THE LIVER. Pediatr Res 8, 382 (1974). https://doi.org/10.1203/00006450-197404000-00252
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DOI: https://doi.org/10.1203/00006450-197404000-00252