title: Identification of a myofibril-bound serine protease and its endogenous inhibitor in mouse skeletal muscle.
abstract: Myofibrillar proteins, like all other intracellular proteins, are in a dynamic state of continual degradation and resynthesis. The proteolytic system responsible for degrading myofibrillar proteins in skeletal muscle is not well defined. A proteolytic activity associated to myofibrils was found in mouse skeletal muscle, as show electrophoretic patterns, and denominated by us, as protease M. During incubation of whole myofibrils at 37 degrees C, myosin heavy chain, alpha actinin, actin and troponin T suffered degradation. These effects were inhibited selectively by serine protease inhibitors (soybean trypsin inhibitor, di-isopropyl phosphofluoridate, phenylmethanesulfonyl fluoride). Using myofibrils as protease M source, azocaseinolytic activity was also detected. Endogenous inhibitor and various compounds effects on protease M activity were also quantified by trichloroacetic acid soluble products formation, using radiolabeled myofibrils. An endogenous trypsin inhibitor isolated from the muscle cytoplasmic fraction could inhibit protease M activity on myofibrillar proteins and on azocasein. While K(+) increased protease M activity, the presence of Ca(2+) did not show any effect. Data presented in this study suggest that reported protease M may be implicated in myofibrillar degradation in vivo and isolated endogenous inhibitor may provide a mechanism to control its action in mouse skeletal muscle.
authors.affiliation: Instituto de Investigaciones Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Casilla de Correo 1245, 7600 Mar del Plata, Argentina.
authors.forename: M P
authors.initials: MP
authors.lastname: Sangorrín
authors.forename: C B
authors.initials: CB
authors.lastname: Martone
authors.forename: J J
authors.initials: JJ
authors.lastname: Sánchez
mesh_terms: D000185:Actinin / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D051379:Mice; D018482:Muscle, Skeletal / Q000737:chemistry / Q000201:enzymology*; D009210:Myofibrils / Q000737:chemistry / Q000201:enzymology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology; D014361:Trypsin Inhibitors / Q000302:isolation & purification* / Q000494:pharmacology
chemical_list: D011480:Protease Inhibitors; D015842:Serine Proteinase Inhibitors; D014361:Trypsin Inhibitors; D000185:Actinin; D012697:Serine Endopeptidases; D018995:Myosin Heavy Chains; D011188:Potassium; D002118:Calcium