Pérez-Rama Mónica, Torres Vaamonde Enrique, Abalde Alonso Julio
Laboratorio de Microbiología, Facultad de Ciencias, Universidade da Coruña, Alejandro de La Sota, No. 1, 15008 La Coruña, Spain.
Environ Toxicol Chem. 2006 Jan;25(1):128-36. doi: 10.1897/05-252r.1.
Time course of intracellular levels of different thiols (phytochelatins, desglycyl-phytochelatins, glutathione, gamma-glutamylcysteine [gamma-Glu-Cys], and cysteine) were studied in the microalga Tetraselmis suecica exposed to different cadmium concentrations for 8 d. The cadmium concentrations assayed were 3, 7.9, 15, and 30 mg/L. Contents of thiol compounds synthesized by this microalga changed with cadmium concentration and with time of exposure. Cysteine concentrations increased significantly compared with those of gamma-Glu-Cys and glutathione in cultures containing 7.9, 15, and 30 mg/L. The increase in the amount of glutathione was significant only in cells exposed to the higher cadmium concentrations (15 and 30 mg/L). Nevertheless, in all the cadmium concentrations assayed, gamma-Glu-Cys levels were constant. A rapid increase in phytochelatins was observed with increased cadmium concentration during the first days of culture. The type of phytochelatins (number of subunits) also was dependent on the concentration of cadmium. The rate of (gamma-Glu-Cys)3-Gly accumulation was higher than those of other types of phytochelatins throughout the culture in cells exposed to 3, 15, and 30 mg/L. However, in cultures treated with 7.9 mg/L, (gamma-Glu-Cys)4-Gly increased substantially after 8 d of culture, exceeding the amount of (gamma-Glu-Cys)3-Gly. Cultures exposed to the higher cadmium concentrations (15 and 30 mg/L) showed a decrease in phytochelatins after 4 and 3 d of culture, respectively, whereas an increase in cysteine and glutathione occurred at the same time. A rapid decrease in phytochelatins also was measured when cells were placed into cadmium-free medium. This decrease is consistent with a degradation of the phytochelatins.
研究了微藻瑞典四爿藻在不同镉浓度下暴露8天期间，不同硫醇（植物螯合肽、去甘氨酰植物螯合肽、谷胱甘肽、γ-谷氨酰半胱氨酸[γ-Glu-Cys]和半胱氨酸）的细胞内水平随时间的变化情况。测定的镉浓度为3、7.9、15和30mg/L。该微藻合成的硫醇化合物含量随镉浓度和暴露时间而变化。在含有7.9、15和30mg/L镉的培养物中，半胱氨酸浓度与γ-Glu-Cys和谷胱甘肽相比显著增加。谷胱甘肽含量仅在暴露于较高镉浓度（15和30mg/L）的细胞中有显著增加。然而，在所有测定的镉浓度下，γ-Glu-Cys水平保持恒定。在培养的最初几天，随着镉浓度的增加，观察到植物螯合肽迅速增加。植物螯合肽的类型（亚基数量）也取决于镉的浓度。在暴露于3、15和30mg/L镉的细胞整个培养过程中，（γ-Glu-Cys）3-Gly的积累速率高于其他类型的植物螯合肽。然而，在用7.9mg/L处理的培养物中，培养8天后（γ-Glu-Cys）4-Gly大幅增加，超过了（γ-Glu-Cys）3-Gly的量。暴露于较高镉浓度（15和30mg/L）的培养物分别在培养4天和3天后植物螯合肽减少，而同时半胱氨酸和谷胱甘肽增加。当细胞置于无镉培养基中时，也检测到植物螯合肽迅速减少。这种减少与植物螯合肽的降解一致。
