title: A particle-associated ATP-dependent proteolytic activity in erythroleukemia cells.
abstract: An ATP-dependent proteolytic activity has been detected in both mouse erythroleukemia (Friend) cells and human (K562) erythroleukemia cells. Exposure of the Friend cells to dimethyl sulfoxide, which stimulates differentiation, increased ATP-dependent proteolysis approximately 2-fold although inducing differentiation in the K562 line had no significant effect on proteolysis. In contrast to the previously described soluble ATP-dependent proteolytic system of reticulocytes, the activity in the more primative erythroid cells is associated with a particulate fraction and is readily sedimentable by centrifugation at 100,000 X g for 1 h. Like the soluble reticulocyte system, the particulate activity requires divalent cation and is inhibited by hemin as well as vanadate. The activity was isolated on a sucrose cushion (30%) and did not appear to be associated with membranes, cytoskeleton, or polysomes. This enzymatic activity which degrades abnormal globin chains may initially reside in a particulate fraction and then become solubilized during erythroid maturation to the reticulocyte stage. Alternatively, the particulate activity may disappear with cell maturation being replaced by a distinct soluble activity. ATP-dependent proteolytic activity is eventually lost with reticulocyte maturation and further aging of erythrocytes.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002364:Caseins / Q000378:metabolism; D002458:Cell Fractionation; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004905:Erythrocyte Aging; D005622:Friend murine leukemia virus; D006427:Hemin / Q000494:pharmacology; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000201:enzymology*; D051379:Mice; D010447:Peptide Hydrolases / Q000097:blood* / Q000302:isolation & purification; D011817:Rabbits; D012156:Reticulocytes / Q000201:enzymology
chemical_list: D002364:Caseins; D006427:Hemin; D000255:Adenosine Triphosphate; D010447:Peptide Hydrolases; D004121:Dimethyl Sulfoxide