title: Hexa- and pentapeptide extension of proalbumin: feedback inhibition of albumin synthesis by its propeptide in isolated hepatocytes and in the cell-free system.
abstract: Addition of the chemically synthesized proalbumin hexapeptide in a concentration of 110 micro M to the medium of isolated rat hepatocytes decreased net albumin synthesis by 12%. The synthesis of other secretory proteins was not altered. A weaker inhibitory effect on albumin synthesis was found for a tetrapeptide, a possible degradation product of the proalbumin hexapeptide. For the uptake of the hexa- and tetrapeptide into the cells, bovine serum albumin is required. In a reticulocyte and in a wheat germ cell-free system a propeptide concentration of 600 micro M inhibited albumin synthesis by 50%, whereas total protein synthesis was inhibited by 19% only, and the synthesis of alpha 1-antitrypsin was not inhibited. These results suggest that the synthesis of preproalbumin is regulated by a feedback mechanism with its propeptide as inhibitor.
mesh_terms: D000818:Animals; D002474:Cell-Free System; D005246:Feedback; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology*; D010944:Plants / Q000378:metabolism; D011132:Polyribosomes / Q000378:metabolism; D011228:Prealbumin / Q000494:pharmacology*; D014176:Protein Biosynthesis / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D012156:Reticulocytes / Q000378:metabolism; D012709:Serum Albumin / Q000235:genetics* / Q000494:pharmacology*; D014908:Triticum / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D011228:Prealbumin; D012709:Serum Albumin; C036840:proalbumin hexapeptide extension