Tanaka K, Ichihara A
Institute for Enzyme Research, University of Tokushima, Japan.
Biochem Biophys Res Commun. 1989 Jan 31;158(2):548-54. doi: 10.1016/s0006-291x(89)80084-1.
Purified proteasomes (large multicatalytic proteinase complexes) were found to be very stable, showing no change in activities or structures during prolonged incubation in medium of pH 7.5 at 37 degrees C. However, on addition of urea they were degraded autocatalytically in a time- and dose-dependent manner, suggesting that destruction of the proteasomal complexes acts as a signal for their autolysis. ATP at a physiological concentration greatly stimulated the urea-dependent breakdown of proteasomes. The autolysis induced by urea was almost completely inhibited by hemin, but not by other protease inhibitors tested, such as leupeptin, chymostation and Ep-475. Thus, autolytic degradation of proteasomes appears to be important for the regulation of enzyme levels in eukaryotic cells.
纯化的蛋白酶体（大型多催化蛋白酶复合物）被发现非常稳定，在pH 7.5的培养基中于37℃长时间孵育期间，其活性和结构均未发生变化。然而，加入尿素后，它们会以时间和剂量依赖性方式自催化降解，这表明蛋白酶体复合物的破坏是其自溶的信号。生理浓度的ATP极大地刺激了尿素依赖性的蛋白酶体分解。尿素诱导的自溶几乎完全被血红素抑制，但不受其他测试的蛋白酶抑制剂（如亮抑酶肽、糜蛋白酶抑制剂和Ep-475）的抑制。因此，蛋白酶体的自溶降解似乎对真核细胞中酶水平的调节很重要。
