Hollnagel H C, Di Mascio P, Asano C S, Okamoto O K, Stringher C G, Oliveira M C, Colepicolo P
Departamento de Bioquímica, Universidade de São Paulo, Brasil.
Braz J Med Biol Res. 1996 Jan;29(1):105-10.
Daily oscillations of both beta-carotene and superoxide dismutase (SOD) activity are related to the intracellular control of reactive oxygen species (ROS). It is well established that ROS are present in all aerobic cells. We studied the marine dinoflagellate Gonyaulax polyedra which has been extensively used as a model to understand the biological clock at the molecular level. beta-Carotene, besides suppressing singlet molecular oxygen (1O2), may act as a photoreceptor pigment in many photosynthetic cells. The levels of beta-carotene during the day phase were shown to be twice as high as during the night phase. The dose-response curve for light-induced carotenoid synthesis was linear for up to 45 min of light exposure, after which night phase cells contained the same levels of beta-carotene as day phase cells. Cells exposed to light pulses at different times during the dark period displayed the highest beta-carotene induction in the middle of the night. SOD activity of cell-free extracts of G. polyedra was three to four times higher during the day. This rhythm continued in cells kept in constant light, indicating that the regulation can be attributed to the cellular circadian clock. No-denaturing polyacrylamide gels revealed the presence of several SOD isoenzymes in G. polyedra, including CuZnSOD and MnSOD. Furthermore, G. polyedra SOD cross-reacts with a polyclonal antibody raised against SOD. In addition to being gene regulated by ROS concentration, G. polyedra SOD expression seems also to be under the control of the biological clock.
β-胡萝卜素和超氧化物歧化酶（SOD）活性的每日振荡与细胞内活性氧（ROS）的控制有关。众所周知，ROS存在于所有需氧细胞中。我们研究了海洋甲藻多甲藻，它已被广泛用作在分子水平上理解生物钟的模型。β-胡萝卜素除了能抑制单线态分子氧（1O2）外，在许多光合细胞中还可能作为一种光受体色素。白天阶段的β-胡萝卜素水平显示是夜间阶段的两倍。光诱导类胡萝卜素合成的剂量反应曲线在光照长达45分钟时呈线性，之后夜间阶段的细胞所含β-胡萝卜素水平与白天阶段的细胞相同。在黑暗期不同时间接受光脉冲照射的细胞，在午夜时分显示出最高的β-胡萝卜素诱导水平。多甲藻无细胞提取物的SOD活性在白天要高出三到四倍。这种节律在持续光照的细胞中持续存在，这表明这种调节可归因于细胞昼夜节律钟。非变性聚丙烯酰胺凝胶显示多甲藻中存在几种SOD同工酶，包括铜锌超氧化物歧化酶（CuZnSOD）和锰超氧化物歧化酶（MnSOD）。此外，多甲藻SOD与针对SOD产生的多克隆抗体发生交叉反应。除了受ROS浓度的基因调控外，多甲藻SOD的表达似乎也受生物钟的控制。
