Flügge U I, Stitt M, Freisl M, Heldt H W
Lehrstuhl für Biochemie der Pflanze, Untere Karspüle 2, 3400 Göttingen, Federal Republic of Germany.
Plant Physiol. 1982 Jan;69(1):263-7. doi: 10.1104/pp.69.1.263.
CO(2) fixation by a suspension of isolated spinach chloroplasts was terminated by turning off the light, and changes of metabolite levels in the chloroplast stroma and the surrounding medium were assayed. Whereas CO(2) fixation comes to a total stop within 15 seconds, a conversion of triose phosphates to heptose, hexose, and pentose monophosphates is found to occur for 1 to 2 minutes afterwards. It seems from these data that an inactivation of fructose and sedoheptulose bisphosphatases proceeds with a lag period. In contrast, the conversion of pentose monophosphates to ribulose 1,5-bisphosphate is inhibited immediately after the stop of illumination. As the stromal level of freely available ATP was not depleted under this condition, these data demonstrate that ribulose 5-phosphate kinase was very rapidly inactivated after darkening of the chloroplasts. Essentially, the same effect is also observed when CO(2) fixation is partially inhibited by addition of moderate concentrations of m-chlorocarbonyl phenylhydrazone, partially uncoupling photophosphorylation. It appears from these results, that the activity of ribulose 5-phosphate kinase is not only regulated by light through the mediation of reduced carriers like thioredoxin but also by alternative parameters, e.g. stromal metabolite levels.
通过关闭光源终止分离的菠菜叶绿体悬浮液中的二氧化碳固定，并检测叶绿体基质和周围介质中代谢物水平的变化。虽然二氧化碳固定在15秒内完全停止，但在此之后发现磷酸丙糖会转化为庚糖、己糖和戊糖单磷酸，持续1至2分钟。从这些数据来看，果糖和景天庚酮糖双磷酸酶的失活存在一个延迟期。相比之下，光照停止后，戊糖单磷酸向核酮糖1,5-二磷酸的转化立即受到抑制。由于在此条件下可自由利用的ATP的基质水平并未耗尽，这些数据表明叶绿体变暗后，磷酸核糖激酶很快就失活了。本质上，当通过添加中等浓度的间氯羰基苯腙部分抑制二氧化碳固定、部分解偶联光磷酸化时，也会观察到相同的效果。从这些结果看来，磷酸核糖激酶的活性不仅通过硫氧还蛋白等还原载体的介导受光调节，还受其他参数调节，例如基质代谢物水平。
