title: Regulation of proteolysis in erythroid cells.
abstract: Reticulocytes contain non-lysosomal ATP dependent proteolytic activity which appears important in degrading abnormal proteins as well as certain organelles. ATP acts to repress an endogenous protease inhibitor activity by a process requiring the polypeptide ubiquitin. Free epsilon amino groups on substrates are important for recognition by the full ATP-dependent system but do not appear necessary for hydrolysis per se suggesting that ubiquitin-substrate conjugates repress the inhibitor. ATP-dependent proteolysis declines markedly with reticulocyte maturation and decreases further to negligible levels with aging of erythrocytes. With cell maturation the inhibitor and protease(s) remain but the ubiquitin-containing fraction is less effective in repressing the inhibitor. Finally, additional control mechanisms selective for certain proteins may exist.
mesh_terms: D000255:Adenosine Triphosphate / Q000097:blood; D000818:Animals; D001798:Blood Proteins / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D010447:Peptide Hydrolases / Q000097:blood*; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism*; D014452:Ubiquitins
chemical_list: D001798:Blood Proteins; D002868:Chromosomal Proteins, Non-Histone; D006454:Hemoglobins; D014452:Ubiquitins; D000255:Adenosine Triphosphate; D010447:Peptide Hydrolases