Mode of action of rabbit skeletal muscle cathepsin B towards myofibrillar proteins and the myofibrillar structure.
1. The mode of degradation of myofibrillar proteins and the structural changes in myofibrils due to the action of cathepsin B highly purified from rabbit skeletal muscle were studied. 2. Cathepsin B degraded myosin heavy chain, actin and troponin T, but not alpha-actinin, tropomyosin, troponin I or troponin C among myofibrillar proteins. 3. Cathepsin B optimally degraded myosin heavy chain, actin and troponin T at around pH 5. Degradation of myosin heavy chain produced 6 fragments, 180,000, 150,000, 87,000, 81,000, 75,000 and 69,000 Da, respectively. Actin was hydrolyzed into fragments of 41,000, 38,000 and 30,000 Da. Troponin T was degraded into fragments of 21,000, 12,000 and 10,000 Da. 4. Cathepsin B caused the fragmentation of myofibrils and disturbance of the lateral arrangement of myofibrils. 5. Cathepsin B partly disintegrated the Z-line and the M-line, and induced disordering of the arrangement of filaments in the I-band.
Matsuishi
M
M
Department of Food Science and Technology, Nippon Veterinary and Animal Science University, Tokyo, Japan.
Matsumoto
T
T
Okitani
A
A
Kato
H
H
D000818:Animals; D002401:Cathepsin B / Q000378:metabolism* / Q000494:pharmacology; D006868:Hydrolysis; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D009124:Muscle Proteins / Q000302:isolation & purification / Q000378:metabolism; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D009210:Myofibrils / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D011817:Rabbits
D009124:Muscle Proteins; D002401:Cathepsin B