Matsukura U, Okitani A, Nishimuro T, Kato H
Biochim Biophys Acta. 1981 Nov 13;662(1):41-7. doi: 10.1016/0005-2744(81)90221-7.
The mode of degradation of myofibrils and their constituent proteins by cathepsin L (EC 3.4.22.15) of rabbit skeletal muscle was studied. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis showed that cathepsin L degraded myosin heavy chain, alpha-actinin, actin, troponin T and troponin I assembled in myofibrils and produced mainly fragments of 160 000 and 30 000 daltons in the acidic pH region. This degradation was most intense around pH 4. Degradation of myosin in the isolated state by cathepsin L resulted in the disappearance of the heavy chain and the decrease of light chains 1, 2 and 3, producing fragments of 160 000, 92 000, 83 000 and 60 000 daltons. The degradation of the heavy chain was most severe at pH 4.2. Cathepsin L degraded actin into fragments of 40 000, 37 000 and 30 000 daltons. This action was most intense at pH 4.7. Tropomyosin was not degraded. Troponin T and troponin I were degraded into fragments of 30 000 and 13 000 daltons at pH 3.7--6.7, which were degraded further into smaller fragments. Troponin C was not degraded. alpha-Actinin was degraded into several fragments, the major one of which showed an Mr of 80 000. This degradation was most intense at pH 3.0--3.5.
研究了兔骨骼肌组织蛋白酶L（EC 3.4.22.15）对肌原纤维及其组成蛋白的降解模式。十二烷基硫酸钠（SDS）-聚丙烯酰胺凝胶电泳显示，组织蛋白酶L降解肌原纤维中组装的肌球蛋白重链、α-辅肌动蛋白、肌动蛋白、肌钙蛋白T和肌钙蛋白I，在酸性pH区域主要产生160000和30000道尔顿的片段。这种降解在pH 4左右最为强烈。组织蛋白酶L对分离状态的肌球蛋白的降解导致重链消失，轻链1、2和3减少，产生160000、92000、83000和60000道尔顿的片段。重链的降解在pH 4.2时最为严重。组织蛋白酶L将肌动蛋白降解为40000、37000和30000道尔顿的片段。这种作用在pH 4.7时最为强烈。原肌球蛋白未被降解。肌钙蛋白T和肌钙蛋白I在pH 3.7 - 6.7时被降解为30000和13000道尔顿的片段，并进一步降解为更小的片段。肌钙蛋白C未被降解。α-辅肌动蛋白被降解为几个片段，其中主要片段的相对分子质量为80000。这种降解在pH 3.0 - 3.5时最为强烈。
