Dice J F, Goldberg A L
Proc Natl Acad Sci U S A. 1975 Oct;72(10):3893-7. doi: 10.1073/pnas.72.10.3893.
Previous studies have shown that in mammalian cells proteins of large molecular weight are degraded more rapidly than small ones. Evidence is presented here that half-lives of proteins are also related to their isoelectric points. A double-isotope method was used to compare degradative rates of soluble proteins separated by isoelectric focusing. In rat liver, skeletal muscle, kidney, and brain, more rapid rates of catabolism were found for acidic protein fractions than for neutral or basic ones. Acidic proteins also tended to be degraded faster in several mouse tissues. A literature survey confirmed this trend. For 22 proteins from rat liver, a highly significant correlation was found between rates of degradation and isoelectric points (r = 0.824; P less than 0.01). This relationship between isoelectric point and half-life appears to be distinct from that between protein size and half-life.
先前的研究表明，在哺乳动物细胞中，大分子蛋白质比小分子蛋白质降解得更快。本文提供的证据表明，蛋白质的半衰期也与其等电点有关。采用双同位素法比较等电聚焦分离的可溶性蛋白质的降解速率。在大鼠肝脏、骨骼肌、肾脏和大脑中，发现酸性蛋白组分的分解代谢速率比中性或碱性蛋白组分更快。在几种小鼠组织中，酸性蛋白也往往降解得更快。文献调查证实了这一趋势。对于来自大鼠肝脏的22种蛋白质，发现降解速率与等电点之间存在高度显著的相关性（r = 0.824；P小于0.01）。等电点与半衰期之间的这种关系似乎与蛋白质大小和半衰期之间的关系不同。
