Cell Biology and Genetics Sections, School of Life Sciences, University of Nebraska, 68588, Lincoln, NE, USA.
Planta. 1980 Jan;149(4):376-83. doi: 10.1007/BF00571173.
Exposure of dark-grown restingEuglena gracilis Klebs var.bacillaris Cori to light, ethanol, or malate produced an increase in the specific activity of fumarase (EC. 4.2.1.2) and succinate dehydrogenase (EC. 1.3.99.1) during the first 8-12 h of exposure to inducer, followed by a decrease in the specific activity of both mitochondrial enzymes between 12 and 72 h. The increased specific activity represented a net increase in the level of active enzyme, and it was dependent upon cytoplasmic protein synthesis. The photoinduction of fumarase required continuous illumination while the subsequent decrease in fumarase specific activity was independent of light. Light had little effect on the ethanol and malate induction of fumarase and succinate dehydrogenase. In the mutant W3BUL, which has no detectable protochlorophyll(ide) and chloroplast DNA, light induced both mitochondrial enzymes and the kinetics of enzyme induction were similar to the induction kinetics in wild-type cells. The induction of mitochondrial enzymes appears to be controlled by a non-chloroplast photoreceptor. Dark-grown resting cells of the plastidless mutant W10SmL have lost the ability to regulate fumarase levels. In this mutant, the specific activity of fumarase fluctuated and light had little effect on these fluctuations, indicating that fumarase synthesis was uncoupled from the nonchloroplast photoreceptor. Ethanol addition produced transient changes in fumarase specific activity in W10SmL indicating that in this mutant, mitochondrial enzymes are still inductible by metabolites. Fumarase synthesis in wild-type cells was not induced in the dark by levulinic acid, a chemical inducer of the breakdown ofEuglena storage carbohydrates. Taken together, our results indicate that the photoinduction of mitochondrial enzyme synthesis is not a result of the photoinduction of carbohydrate breakdown. The mechanisms by which light and organic carbon induce the synthesis ofEuglena mitochondria may differ.
黑暗中生长的休止期 Euglena gracilis Klebs var. bacillaris Cori 在暴露于光、乙醇或苹果酸后，在暴露于诱导剂的前 8-12 小时内，琥珀酸脱氢酶（EC 1.3.99.1）的比活性增加，随后在 12-72 小时之间，两种线粒体酶的比活性下降。增加的比活性代表活性酶水平的净增加，并且依赖于细胞质蛋白质合成。琥珀酸脱氢酶的光诱导需要连续光照，而随后琥珀酸脱氢酶比活性的下降与光照无关。光照对乙醇和苹果酸诱导的琥珀酸脱氢酶和琥珀酸脱氢酶的影响很小。在没有可检测的原叶绿素（ide）和叶绿体 DNA 的突变体 W3BUL 中，光诱导了两种线粒体酶，并且酶诱导的动力学与野生型细胞中的诱导动力学相似。线粒体酶的诱导似乎由非叶绿体光受体控制。没有质体的突变体 W10SmL 的黑暗生长静止细胞已经失去了调节琥珀酸脱氢酶水平的能力。在这个突变体中，琥珀酸脱氢酶的比活性波动，光照对这些波动影响很小，表明琥珀酸脱氢酶的合成与非叶绿体光受体解耦。乙醇的添加导致 W10SmL 中琥珀酸脱氢酶比活性的瞬时变化，表明在这个突变体中，线粒体酶仍然可以被代谢物诱导。在黑暗中，Euglena 储存碳水化合物分解的化学诱导剂戊酸并没有诱导野生型细胞中琥珀酸脱氢酶的合成。总的来说，我们的结果表明，线粒体酶合成的光诱导不是碳水化合物分解的光诱导的结果。光和有机碳诱导 Euglena 线粒体合成的机制可能不同。
