Seftor R E, Jensen R G
Department of Biochemistry, University of Arizona, Tucson, Arizona 85721.
Plant Physiol. 1986 May;81(1):81-5. doi: 10.1104/pp.81.1.81.
When isolated spinach chloroplasts are illuminated, photosynthesis and CO(2) fixation die off within 30 to 90 minutes. Even when air levels of CO(2) are used which maintain high and rate-saturating amounts of ribulose 1,5-bisphosphate inside the plastids, CO(2) fixation declines. The decline begins with a drop in activity of the ribulose 1,5-bishosphate carboxylase/oxygenase, specifically loss of the enzyme-activator CO(2)-Mg(2+) form. Next, the light reactions cause gradual leakage of the carboxylase and other stromal proteins to the suspending medium. The chloroplast outer envelope appears to reseal and protect the thylakoids since there is little change in the ferricyanide-dependent Hill reaction. In the dark, under otherwise identical conditions, leakage of carboxylase does not occur.
当分离出的菠菜叶绿体受到光照时，光合作用和二氧化碳固定在30到90分钟内就会停止。即使使用空气中的二氧化碳水平，以维持质体内高浓度且速率饱和的1,5-二磷酸核酮糖，二氧化碳固定仍会下降。下降始于1,5-二磷酸核酮糖羧化酶/加氧酶活性的降低，特别是该酶的激活剂二氧化碳-镁离子形式的丧失。接下来，光反应导致羧化酶和其他基质蛋白逐渐泄漏到悬浮介质中。叶绿体的外膜似乎会重新封闭并保护类囊体，因为依赖铁氰化物的希尔反应几乎没有变化。在黑暗中，在其他条件相同的情况下，羧化酶不会发生泄漏。
