Ricin-binding properties of acid hydrolases from isolated lysosomes implies prior processing by terminal transferases of the trans-Golgi apparatus.
Acid hydrolases were isolated from the lysosome fraction of beta-galactosidase-deficient human fibroblasts and from the mannose 6-phosphate containing medium in which they were grown. Nearly half of the total beta-hexosaminidase and beta-glucuronidase from both sources bound to Ricin specifically. Lysosomal beta-hexosaminidase, metabolically labelled with [35S]-methionine, was also fractionated on Ricin-agarose. SDS-PAGE of immunoprecipitates from Ricin-binding and non-binding fractions revealed approximately equivalent amounts of cross-reacting material at the appropriate MW. We interpret these results to mean that acid hydrolases which are segregated to lysosomes are exposed to trans-Golgi processing enzymes to about the same extent as enzymes which are secreted, and that segregation by the Man 6-P receptor occurs after transit through the trans-Golgi compartment.
D001665:Binding Sites; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D005347:Fibroblasts / Q000201:enzymology; D005677:G(M1) Ganglioside; D005733:Gangliosidoses / Q000201:enzymology; D005966:Glucuronidase / Q000378:metabolism; D006056:Golgi Apparatus / Q000201:enzymology*; D006596:Hexosaminidases / Q000378:metabolism; D006801:Humans; D006867:Hydrolases / Q000378:metabolism*; D007120:Immunochemistry; D008247:Lysosomes / Q000201:enzymology*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D012276:Ricin / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism*; D001619:beta-N-Acetylhexosaminidases
D005677:G(M1) Ganglioside; D012276:Ricin; D014166:Transferases; D006867:Hydrolases; D006596:Hexosaminidases; D005966:Glucuronidase; D001619:beta-N-Acetylhexosaminidases