Kern G, Kern D, Schmid F X, Fischer G
Max-Planck-Arbeitsgruppe Enzymologie der Peptidbindung, Halle/Saale, Germany.
FEBS Lett. 1994 Jul 11;348(2):145-8. doi: 10.1016/0014-5793(94)00591-5.
The folding of proteins can be assisted by two unrelated groups of helper molecules. Chaperones suppress non-productive side reactions by stoichiometric binding to folding intermediates, and folding enzymes catalyze slow rate-limiting steps of folding. We reinvestigated, whether peptidyl-prolyl-cis/trans-isomerases of the cyclophilin type act simultaneously as chaperones and as folding catalysts in the reactivation of human carbonic anhydrase II, as reported recently [Freskgård, P.-O. et al. (1992) Science 258, 466-468; Rinfret, A. et al. (1994) Biochemistry 33, 1668-1673]. No increase in the yield of native carbonic anhydrase-II could be detected in the presence of three different prolyl isomerases, when reactivation was followed by a sensitive assay for an extended time of 4 h. We conclude that the role of prolyl isomerases in the refolding of carbonic anhydrase can be explained solely by their isomerase activity. There is no need to invoke simultaneous functions as chaperones for these folding catalysts.
蛋白质的折叠可由两类不相关的辅助分子协助完成。伴侣蛋白通过与折叠中间体进行化学计量结合来抑制非生产性副反应，而折叠酶则催化折叠过程中缓慢的限速步骤。我们重新研究了亲环蛋白类型的肽基脯氨酰顺反异构酶是否如最近报道的那样，在人碳酸酐酶II的再活化过程中同时作为伴侣蛋白和折叠催化剂发挥作用[弗雷斯科加德，P.-O.等人（1992年）《科学》258卷，466 - 468页；林弗雷特，A.等人（1994年）《生物化学》33卷，1668 - 1673页]。当用灵敏的检测方法对再活化过程进行长达四小时的延长时间跟踪时，在三种不同的脯氨酰异构酶存在的情况下，未检测到天然碳酸酐酶II的产量增加。我们得出结论，脯氨酰异构酶在碳酸酐酶重折叠中的作用仅可由其异构酶活性来解释。无需将这些折叠催化剂同时看作是具有伴侣蛋白功能。
