title: Turnover of the creatine kinase subunits in chicken myogenic cell cultures and in fibroblasts.
abstract: The rates of degradation of creatine kinase subunits, M-CK and B-CK subunits, were measured in cultured myogenic cells and in subcultured fibroblasts. In differentiated myogenic cells, the myotubes, both M-CK and B-CK subunits are synthesized. Their rates of degradation were compared. The M-CK subunits is slightly more stable and is degraded with an average apparent half-life of 75 h, whereas that of the B-CK subunit was shorter with 63 h. The turnover properties of M-CK subunit from soluble and of myofibril-bound MM-CK homodimeric creatine kinase isoenzyme isolated from breast muscle of young chickens were identical. The apparent half-life of the B-CK subunit was also determined in subcultured fibroblasts and 5-bromo-2'-deoxyuridine-treated cells, and found to be shorter than in myotubes (46 h and 37 h respectively). Similar observations were made for myosin heavy chain, actin and total acid-precipitable material. It appears therefore that proteins are in general degraded more slowly in differentiated myogenic cells. The differences in the stability of M-CK and B-CK subunits in myotubes probably do not reflect a major regulatory mechanism of the creatine kinase isoenzyme transition.
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D002642:Chick Embryo; D003402:Creatine Kinase / Q000378:metabolism*; D005347:Fibroblasts / Q000201:enzymology; D006207:Half-Life; D007527:Isoenzymes; D009124:Muscle Proteins / Q000378:metabolism; D009132:Muscles / Q000166:cytology / Q000196:embryology / Q000201:enzymology*; D009218:Myosins / Q000378:metabolism
chemical_list: D000199:Actins; D007527:Isoenzymes; D009124:Muscle Proteins; D003402:Creatine Kinase; D009218:Myosins