title: Mode of degradation of myofibrillar proteins by rabbit muscle cathepsin D.
abstract: The mode of degradation of myofibrillar proteins by the action of highly purified rabbit muscle cathepsin D (EC 3.4.23.5) was studied using SDS-polyacrylamide gel electrophoresis. Cathepsin D optimally degraded myosin heavy chain, alpha-actinin, tropomyosin, troponin T and troponin I at around pH 3. It did not degrade actin or troponin C. Degradation of myosin heavy chain produced four major fragments of 155000, 130000, 110000 and 90000 daltons. Troponin T was hydrolyzed to 33000-, and 20000- and 11000-dalton fragments. Troponin I was degraded into fragments of 13000 and 11000 daltons. Degradation of alpha-actinin and tropomyosin was not as rapid as that of myosin and troponins T and I. Tropomyosin gave a fragment of 30000 daltons, but alpha-actinin showed no distinct band of this fragment on gels.
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002402:Cathepsin D; D002403:Cathepsins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D008970:Molecular Weight; D009124:Muscle Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009132:Muscles / Q000201:enzymology*; D009210:Myofibrils / Q000378:metabolism; D011817:Rabbits; D014336:Troponin / Q000378:metabolism
chemical_list: D000199:Actins; D009124:Muscle Proteins; D014336:Troponin; D002403:Cathepsins; D002402:Cathepsin D