United States Department of Agriculture, Agricultural Research Service, 1102 South Goodwin Avenue, Urbana, Illinois 61801.
Plant Physiol. 1986 Dec;82(4):967-71. doi: 10.1104/pp.82.4.967.
The enzyme-catalyzed activation of ribulosebisphosphate carboxylase/oxygenase (rubisco) was investigated in an illuminated reconstituted system containing thylakoid membranes, rubisco, ribulosebisphosphate (RuBP), MgCl(2), carbonic anhydrase, catalase, the artificial electron acceptor pyocyanine, and partially purified rubisco activase. Optimal conditions for light-induced rubisco activation were found to include 100 micrograms per milliliter rubisco, 300 micrograms per milliliter rubisco activase, 3 millimolar RuBP, and 6 millimolar free Mg(2+) at pH 8.2. The half-time for rubisco activation was 2 minutes, and was 4 minutes for rubisco deactivation. The rate of rubisco deactivation was identical in the presence and absence of activase. The K(act)(CO(2)) of rubisco activation in the reconstituted system was 4 micromolar CO(2), compared to a K(act)(CO(2)) of 25 to 30 micromolar CO(2) for the previously reported spontaneous CO(2)/Mg(2+) activation mechanism. The activation process characterized here explains the high degree of rubisco activation at the physiological concentrations of 10 micromolar CO(2) and 2 to 4 millimolar RuBP found in intact leaves, conditions which lead to almost complete deactivation of rubisco in vitro.
在一个含有类囊体膜、Rubisco、RuBP、MgCl2、碳酸酐酶、过氧化氢酶、人工电子受体吡咯并喹啉醌以及部分纯化的 Rubisco 激活酶的光照重组系统中，研究了核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco）的酶促激活。发现光诱导 Rubisco 激活的最佳条件包括：Rubisco 浓度为 100 微克/毫升，Rubisco 激活酶浓度为 300 微克/毫升，RuBP 浓度为 3 毫摩尔，游离 Mg2+浓度为 6 毫摩尔，pH 值为 8.2。Rubisco 激活的半衰期为 2 分钟，失活半衰期为 4 分钟。在有或没有激活酶的情况下，Rubisco 的失活速率相同。在重组系统中，Rubisco 激活的 Kact(CO2)为 4 微摩尔 CO2，而之前报道的自发 CO2/Mg2+激活机制的 Kact(CO2)为 25 至 30 微摩尔 CO2。这里描述的激活过程解释了在完整叶片中发现的生理浓度 10 微摩尔 CO2 和 2 至 4 毫摩尔 RuBP 条件下 Rubisco 高度激活的原因，在这些条件下，Rubisco 在体外几乎完全失活。
