Degradation of [6-3H]- and [1-14C]glucosamine-labeled asialo-alpha 1-acid glycoprotein by the perfused rat liver.

摘要: We studied the degradation and metabolism of radioactive glucosamine-labeled asialo-alpha 1-acid glycoprotein by perfused rat liver. Removal 130 micrograms protein from perfusate occurred with a T 1/2 10.3 min. Radioactivity associated initially microsomal fraction tissue homogenate was then transferred to lysosomes where hydrolysis N-acetylglucosamine residues took place. left lysosomal-rich 50 Final accumulation radioactivity in supernatant greater than 80% this material found be UDP-N-acetylhexosamines. In those studies, 10 mumol unlabeled glucosamine had been added expand intracellular pool UDP-GlcNAc prevent further any released lysosomes. When procedure not done, one-third lysosomally derived reused liver form new glycoproteins secreted into perfusate. Overall substrate during 2 h perfusion. However, leupeptin, thiol cathepsin inhibitor, decreased release amino sugar 50%, even though compound no effect on activity lysosomal glycosidase vitro. Large glycopeptides molecular weight 35,000 accumulated due leupeptin. From these we conclude that efficient digestion carbohydrate component situ requires concerted both glycosidases proteases.