Goicoechea S M, Tabares M L, Sabas M E, Pucciarelli M G, Conde R D
Instituto de Investigationes Biologicas, Facultad de Ciencies Exactas y Naturales, Universidad Nacional de Mar del Plata, Argentina.
Horm Metab Res. 1994 Apr;26(4):175-80. doi: 10.1055/s-2007-1000806.
The effect of protein depletion and refeeding with a normal diet on mouse liver soluble homogenate calpain activity was studied. It was unchanged when expressed in terms of whole liver (units/liver). However, when expressed in terms of degradable protein (units/mg protein) it increased with depletion and decreased with refeeding. DEAE Sephacel chromatography of soluble homogenate yielded three calpain activities which were eluted at 0.04, 0.16 and 0.23 M NaCl, respectively. On the basis of whole liver, they decreased with depletion and increased with refeeding. Immunochemical analysis revealed similar changes in the mass of the calpain eluted with 0.16 M NaCl. The sum of these three activities (total liver calpain activity) was higher than the activity displayed by the soluble homogenate, indicating that they were separated from calpastatin. Furthermore, the percentage of total calpain activity displayed by soluble homogenate increased with depletion and decreased with refeeding, suggesting that depleted liver had the lowest calpastatin content. This was confirmed by direct measurements which indicated that depleted homogenate had in average 5.5 and 3.1 times less calpastatin compared to normal and 16 hours refed liver, respectively. It is concluded that a remarkable decrease in calpastatin content maintained unchanged whole liver soluble homogenate calpain activity during protein depletion and refeeding and contributes to an increased calpain activity related to degradable protein in depleted livers. This increase is in accordance with the high in vivo rate of protein breakdown depicted by these livers.
研究了蛋白质耗竭及再给予正常饮食对小鼠肝脏可溶性匀浆钙蛋白酶活性的影响。以全肝表示（单位/肝脏）时，其活性未发生变化。然而，以可降解蛋白质表示（单位/毫克蛋白质）时，它随蛋白质耗竭而增加，随再喂养而降低。对可溶性匀浆进行二乙氨基乙基纤维素（DEAE Sephacel）层析得到三种钙蛋白酶活性，它们分别在0.04、0.16和0.23M氯化钠浓度下被洗脱。以全肝为基础，它们随蛋白质耗竭而降低，随再喂养而增加。免疫化学分析显示，用0.16M氯化钠洗脱的钙蛋白酶质量也有类似变化。这三种活性之和（肝脏总钙蛋白酶活性）高于可溶性匀浆所显示的活性，表明它们与钙蛋白酶抑制蛋白分离。此外，可溶性匀浆所显示的总钙蛋白酶活性百分比随蛋白质耗竭而增加，随再喂养而降低，这表明蛋白质耗竭的肝脏中钙蛋白酶抑制蛋白含量最低。直接测量结果证实了这一点，结果表明，与正常肝脏和再喂养16小时的肝脏相比，蛋白质耗竭的匀浆中钙蛋白酶抑制蛋白平均分别少5.5倍和3.1倍。得出的结论是，在蛋白质耗竭及再喂养过程中，钙蛋白酶抑制蛋白含量显著降低，使得全肝可溶性匀浆钙蛋白酶活性保持不变，并导致蛋白质耗竭肝脏中与可降解蛋白质相关的钙蛋白酶活性增加。这种增加与这些肝脏所呈现的体内高蛋白分解率相一致。
