Kirwin P M, Elderfield P D, Robinson C
Department of Biological Sciences, University of Warwick, Coventry, Great Britain.
J Biol Chem. 1987 Dec 5;262(34):16386-90.
Plastocyanin is synthesized in the cytoplasm as a larger precursor and transported across three membranes into the chloroplast thylakoid lumen. Processing to the mature size involves successive cleavages by a stromal and a thylakoidal peptidase. In this report we describe the partial purification and characterization of the thylakoidal peptidase involved. The enzyme has been purified 36-fold from Pisum sativum thylakoids after solubilization using Triton X-100. The peptidase processes the plastocyanin import intermediate to the mature size, but no further, and is capable of processing pre-plastocyanin to the mature size but at a lower rate. No detectable activity is displayed against non-chloroplast proteins or precursors of stromal proteins. The enzyme has a pH optimum of 6.5-7 and is activated by chelating agents such as EDTA and EGTA. No inhibitors of the peptidase have been found to date.
质体蓝素在细胞质中作为一种较大的前体被合成，然后穿过三层膜进入叶绿体类囊体腔。加工成成熟大小涉及由一种基质肽酶和一种类囊体肽酶相继进行切割。在本报告中，我们描述了所涉及的类囊体肽酶的部分纯化和特性。使用 Triton X-100 溶解后，该酶已从豌豆类囊体中纯化了 36 倍。该肽酶将质体蓝素导入中间体加工成成熟大小，但不会进一步加工，并且能够将前质体蓝素加工成成熟大小，但速率较低。对非叶绿体蛋白或基质蛋白前体没有可检测到的活性。该酶的最适 pH 为 6.5 - 7，并被 EDTA 和 EGTA 等螯合剂激活。迄今为止尚未发现该肽酶的抑制剂。
