Laboratory of Plant Pigment Biochemistry and Photobiology, 240A PABL, 1201 West Gregory, University of Illinois, Urbana, Illinois 61801.
Plant Physiol. 1992 Jul;99(3):1134-40. doi: 10.1104/pp.99.3.1134.
The preparation from Percoll-purified cucumber (Cucumis sativus)etiochloroplasts of a subplastidic membrane fraction that is capable of high rates of Mg insertion into protoporphyrin IX is described. The plastid stroma was inactive when used either alone or in combination with the membrane fraction. Successful preparation of the subplastidic membrane fraction required that Mg-protoporphyrin chelatase was first stabilized by its substrate. This was achieved by lysing Percoll-purified plastids in a fortified hypotonic medium containing protoporphyrin IX prior to ultracentrifugation and separation of the stroma from the plastid membranes. Protoporphyrin IX became membrane bound. Other additives needed for enzyme activity fell into two groups: (a) those needed for enzyme stabilization during membrane preparation and (b) those involved in the primary mechanism of Mg insertion into protoporphyrin IX. Ethylenediaminetetraacetate belonged to the first group, magnesium belonged to the second group, and ATP belonged to both groups.
从经过 Percoll 纯化的黄瓜（Cucumis sativus）叶绿体中制备了一种亚质膜部分，该部分能够将镁高效插入原卟啉 IX。当单独使用或与膜部分结合使用时，质体基质均无活性。成功制备亚质膜部分需要首先通过其底物稳定镁原卟啉螯合酶。这是通过在超速离心和质体膜与基质分离之前，在含有原卟啉 IX 的强化低渗介质中裂解 Percoll 纯化的质体来实现的。原卟啉 IX 成为膜结合物。酶活性所需的其他添加剂分为两类：（a）在膜制备过程中稳定酶所需的添加剂，以及（b）参与镁插入原卟啉 IX 的主要机制的添加剂。乙二胺四乙酸属于第一类，镁属于第二类，而 ATP 属于两类。
