THE 20S/26S PROTEASOMAL PATHWAY OF PROTEIN-DEGRADATION IN MUSCLE-TISSUE
THE 20S/26S PROTEASOMAL PATHWAY OF PROTEIN-DEGRADATION IN MUSCLE-TISSUE
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DOI：
10.1007/bf00990972
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发表时间：
1995-01-01
影响因子：
2.8
通讯作者：
KUEHN, L
中科院分区：
文献类型：
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作者：
DAHLMANN, B;KUEHN, L
与所有其他真核细胞和组织类似，肌肉组织含有20 S/26 S蛋白酶体的蛋白水解系统，其中20 S蛋白酶体主要以潜伏状态存在。与哺乳动物酶不同，从几种鱼类和龙虾的肌肉中分离的20 S蛋白酶体的体外从潜伏状态到活化状态的转变可以通过热休克实现。20 S蛋白酶体的活化状态很可能对应于酶的生理活性形式，因为只有该酶才能在任何显著程度上攻击肌浆蛋白和肌原纤维蛋白。由于灌流大鼠后躯与假定的低分子量激活剂，如游离脂肪酸不会导致肌肉蛋白酶体的激活，其他可能的蛋白质激活剂-可能在体内起到这一作用。26 S蛋白酶体复合物可以被认为是这样的蛋白酶体/激活剂复合物。26 S蛋白酶体复合物具有通过ATP消耗反应降解蛋白质（-泛素-缀合物）的能力。由于增加量的泛素化蛋白质以及增强的活性的ATP（-泛素）依赖性蛋白水解系统已被测量在大鼠肌肉组织在各种分解代谢条件下，这是不可能的，这条途径是负责催化肌肉蛋白质分解。
Similar to all other eukaryotic cells and tissues muscle tissue contains the proteolytic system of 20S/26S proteasomes with the 20S proteasome existing predominantly in a latent state. Unlike with the mammalian enzyme in vitro transition from the latent to the activated state of the 20S proteasomes isolated from muscle of several fish species and from lobster can be achieved by heat shock. It is very likely that the activated state of the 20S proteasome corresponds to the physiologically active form of the enzyme since only that one is able to attack sarcoplasmic and myofibrillar proteins to any significant extent. As perfusion of rat hindquarters with presumptive low molecular mass activators like free fatty acids does not result in an activation of the muscle proteasome other - possibly protein activators - may serve this purpose in vivo. The 26S proteasome complex may be regarded as such a proteasome/activator complex. The 26S proteasome complex has the ability to degrade protein (-ubiquitin-conjugates) by an ATP-consuming reaction. Since increased amounts of ubiquitinated proteins as well as an enhanced activity of the ATP (-ubiquitin)-dependent proteolytic system have been measured in rat muscle tissue during various catabolic conditions, it is not unlikely that this pathway is responsible for catalysis of muscle protein breakdown.