title: Elevated levels of a calcium-activated muscle protease in rapidly atrophying muscles from vitamin E-deficient rabbits.
abstract: A Ca2+-activated proteolytic enzyme that partially degrades myofibrils was isolated from hind limb muscles of normal rabbits and rabbits undergoing rapid muscle atrophy as a result of vitamin E deficiency. Extractable Ca2+-activated protease activity was 3.6 times higher in muscle tissue from vitamin E-deficient rabbits than from muscle tissue of control rabbits. Ultrastructural studies of muscle from vitamin E-deficient rabbits showed that the Z disk was the first myofibrillar structure to show degradative changes in atrophying muscle. Myofibrils prepared from muscles from vitamin E-deficient rabbits showed partial or complete loss of Z-disk density. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that the amount of troponin-T (37 000 daltons) and alpha-actinin (96 000 daltons) was reduced in myofibrils from atrophying muscle as compared to myofibrils prepared from control muscle. In vitro treatment of purified myofibrils with purified Ca2+-activated proteolytic enzyme produced alterations in myofibrillar ultrastructure that were identical to the initial alterations occurring in myofibrils from atrophying muscle (i.e. weakening and subsequent removal of Z disks). Additonally the electrophoretic banding pattern of Ca2+-activated proteolytic enzyme-treated myofibrils is very similar to that of myofibrils prepared from muscles atrophying as a result of nutritional vitamin E deficiency. The possible role of Ca2+-activated proteolytic enzyme in disassembly and degradation of the myofibril is discussed.
mesh_terms: D000818:Animals; D001284:Atrophy / Q000201:enzymology; D002118:Calcium / Q000494:pharmacology*; D004789:Enzyme Activation; D008297:Male; D009132:Muscles / Q000201:enzymology* / Q000473:pathology; D009210:Myofibrils / Q000201:enzymology / Q000648:ultrastructure; D010447:Peptide Hydrolases / Q000378:metabolism*; D011817:Rabbits; D014811:Vitamin E Deficiency / Q000201:enzymology* / Q000473:pathology
chemical_list: D010447:Peptide Hydrolases; D002118:Calcium