不同培养条件下锰过氧化物酶(MnP)的合成及其对甲基橙的降解

高效、大规模、低成本合成木质素降解酶是直接采用其降解难降解有机污染物所必须解决的问题.对锰过氧化物酶(MnP)降解甲基橙和在非灭菌的反应器中连续合成MnP的可行性进行考察.结果表明,在采用2 mmol H2O2和1.5 mmol MnSO4的降解体系中,获最大脱色效果,且100、200和300 U/L的MnP可在8h内将甲基橙分别脱色18％、23％和35％;在非灭菌的反应器水平上实现了固定化培养的P.chrysosporium连续23 d合成MnP,但MnP酶活仅为2～ 23 U/L,难以酶解甲基橙;然而,在摇瓶培养条件下固定化的P.chrysosporium合成的MnP却能达1 152 U/L.因此,直接采用MnP对污染物进行降解以及在非灭菌的反应器中持续合成MnP是可行的,但就在非灭菌条件下如何提高MnP的合成量还有待开展深入的研究.     

Response of the Ascorbate-Peroxidase of Selenastrum capricornutum to Copper and Lead in Stormwaters

The green alga Selenastrum capricornutum expresses a uniqueascorbate peroxidase, that responds to copper and lead. Attemptswere made to test if this peroxidase could be used to monitor thelevels of copper and lead in natural waters. When S.capricornutum was exposed to a stormwater sample, the specificactivity of the peroxidase in the cell extract was commensuratewith the combined copper and lead contents in the sample. Theperoxidase responses were also correlated with the 96 hr biomasstoxicity assay of S. capricornutum. However, unlike thebiomass toxicity assay, the peroxidase activity was not affectedby the anions in the samples. The use of this peroxidase can beused as a marker for testing heavy metal toxicity in the water.     

久效磷对海洋微藻毒性机理的初步研究Ⅲ.超氧化物歧化酶和过氧化物酶活性的变化

报道了久效磷对３种海洋微藻细胞内２种清除活性氧的关键性酶－超氧化物歧化酶和过氧化酶活性的影响。结果显示：１．在久效磷的胁迫下，扁藻和三角褐指藻细胞的超化物歧化酶活性均表现出下降的总变化趋势，而叉鞭金藻细胞的ＳＯＤ活性时而上升，时而下降，在整个胁迫过程中呈现出无规律性的变化。２．随着久铲磷胁迫时间的延长，３种微藻细胞的过氧化酶活性均逐渐下降，表现出相同的变化规律性。     

土壤重金属污染的酶学诊断——紫色土中的镉、铜、铅、砷对水稻根系过氧化物酶的影响

通过四川酸性紫色土、中性紫色土,石灰性紫色土中不同浓度的Cd、Cu、Pb、As对水稻根系过氧化物酶的影响研究,揭示了过氧化物酶受抑制与产生抗性的过程.在低浓度时,上述元素对过氧化物酶的影响能反映土壤类型影响的差别.确定了三种紫色土中Cd、Cu、Pb、As的临界浓度.     

Plant steroid hormones produced under Ni stress are involved in the regulation of metal uptake and oxidative stress in Brassica juncea L

Brassinosteroids (BRs) are involved in the amelioration of various biotic and abiotic stresses. With an aim to explore the role of BRs under heavy metal stress, plants of Brassica juncea L. were grown in pots. The plants were subjected to various concentrations of Nickel metal (0.0, 0.2, 0.4 and 0.6 mM) and harvested on 60th day in order to observe the expression of these hormones. The isolated BRs from the leaves of Brassica plants characterized by GC-MS include 24-Epibrassinolide (24-EBL), Castasterone, Dolicholide and Typhasterole. The effect of isolated 24-EBL was studied on Ni metal uptake and antioxidative defense system in 60 d old plants of Brassica. It was observed that 24-EBL significantly increased the activities of stress ameliorating enzymes and lowered the metal uptake in plants. This is the first report in B. juncea L. plants showing the expression of BRs under metal treatments and effect of the isolated 24-EBL on metal uptake and in oxidative stress management.     

Degradation of direct azo dye by Cucurbita pepo free and immobilized peroxidase

Enzymatic decolourization of the azo dye, Direct Yellow (DY106) by Cucurbita pepo (courgette) peroxidase (CP) is a complex process, which is greatly affected by pH, temperature, enzyme activity and the concentrations of H₂O₂ and dye. Courgette peroxidase was extracted and its performance was evaluated by using the free-CP (FCP) and immobilized-CP (ICP) forms in the decolourization of DY106. Immobilization of peroxidase in calcium alginate beads was performed according to a strategy aiming to minimize enzyme leakage and keep its activity at a maximum value by optimizing sodium alginate content, enzyme loading and calcium chloride concentration. The initial conditions at which the highest DY106 decolourization yield was obtained were found at pH 2, temperature 20℃, H₂O₂ dose 1 mmol/L (FCP) and 100 mmol/L (ICP). The highest decolourization rates were obtained for dye concentrations 50 mg/L (FCP) and 80 mg/L (ICP). Under optimal conditions, the FCP was able to decolorize more than 87% of the dye within 2 min. While with ICP, the decolourization yield was 75% within 15 min. The decolourization and removal of DY106 was proved by UV-Vis analysis. Fourier transform infrared (FT-IR) spectroscopy analysis was also performed on DY106 and enzymatic treatment precipitated byproduct.     

镉胁迫对虾夷扇贝抗氧化防御系统的影响

实验研究了虾夷扇贝在96 h的急性毒性效应,以及不同浓度Cd2+(0,0.005,0.025,0.050,0.150和0.300 mg/L)对虾夷扇贝内脏团超氧化物岐化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽-过氧化物酶(GSH-PX)活力的影响,以探讨其用于污染暴露的生物标记的可行性。结果表明:虾夷扇贝96 h的LC50为1.73 mg/L;其95%的置信区间是1.58～1.90 mg/L;安全浓度为0.0173 mg/L。酶活力:0.025 mg/L及以上的各实验组SOD活力先上升后下降,在第3 d时达到峰值,与对照组呈显著差异(P<0.05);处理第6 d,各浓度组SOD活力有所下降,到第9 d时受到抑制;CAT活力在处理0.5 d时,0.025mg/L0、.150 mg/L和0.300 mg/L三个浓度组均受到显著诱导(P<0.05),处理第6 d时,各实验组酶活力开始受到抑制。两种酶对实验设计的Cd2+浓度反应敏感,呈现出"诱导-抑制"规律,对海洋Cd2+早期污染具有指示作用。GSH-PX对Cd2+污染没有SOD和CAT那样敏感,GSH-PX的各个实验组与对照组相比差异均不显著,因而它作为对海洋Cd2+早期污染指示物的意义不大。     

Accumulation of mercury and its effect on antioxidant enzymes in brain,liver, and kidneys of mice

Abstract

The effect of mercuric chloride (HgCl₂) on the activities of catalase, Superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) and its effect on glutathione (GSH) content were evaluated in different organs (liver, kidneys, and brain) of mice after administration at 0, 0.25, 0.5 and 1.0 mg/kg/day for 14 days. The uptake of mercury shows that the kidneys accumulated the highest levels of mercury compare to brain and liver. The enzyme levels varied in mercury treated organs compare to control. A dose dependent increase of antioxidant enzymes occurred in the liver and kidneys. The increase in enzyme activities correlated with highest mercury accumulation in the kidneys and liver. Mercury is known to generate reactive oxygen species (ROS) in vivo and in vitro, therefore, it is likely that enzyme activities increased to scavenge ROS levels produced as a result of mercury accumulation. Glutathione content increased in liver and kidneys of mercury treated mice compare to control. The results showed that the highest oral dose of mercury significantly increased antioxidant enzymes in kidneys and liver. The increased antioxidant enzymes enhance the antioxidant potential of the organs to reduce oxidative stress.     

Peroxidase-mediated removal of endocrine disrupting compound mixtures from water

Several classes of oxidative enzymes have shown promise for efficient removal of endocrine disrupting compounds (EDCs) that are resistant to conventional wastewater treatments. Although the kinetics of reactions between individual EDCs and selected oxidative enzymes are well documented in the literature, there has been little investigation of reactions with EDC mixtures. This makes it impossible to predict how enzyme-mediated treatment systems will perform since wastewater effluents generally contain multiple EDCs. This paper reports pseudo-first order rate constants for a model oxidative enzyme, horseradish peroxidase (HRP), during single-substrate (k₁) and mixed-substrate (k_1-MIX) reactions. Measured values are compared with literature values of three Michaelis-Menten parameters: half-saturation constant (K_M), enzyme turnover number (k_CAT), and the ratio k_CAT/K_M. Published reports had suggested that each of these could be correlated with HRP reactivity towards EDCs in mixtures, and empirical results from this study show that K_M can be used to predict the sequence of EDC removal reactions within a particular mixture. We also observed that k_1-MIX values were generally greater than k₁ values and that compounds exhibiting greatest estrogenic toxicities reacted most rapidly in a given mixture. Finally, because K_M may be tedious to measure for every EDC of interest, we have constructed a quantitative structure-activity relationship (QSAR) model to predict these values. This model predicts K_M quite accurately (R² = 89%) based on two molecular characteristics: molecular volume and hydration energy. Its accuracy makes this QSAR a useful tool for predicting which EDCs will be removed most efficiently during enzyme treatment of EDC mixtures.     

突变灰盖鬼伞过氧化物酶降解刚果红的响应面法优化分析简

酶法降解偶氮染料刚果红是一个复杂的过程，受温度、pH、酶量、刚果红浓度和双氧水浓度显著影响。为研究各因素及因素间交互作用对刚果红降解影响，提高刚果红的降解率，分别使用单因素法和响应面分析法对刚果红降解条件进行了优化。单因素实验结果显示灰盖鬼伞过氧化物酶降解刚果红的最适条件为：pH 5.0、32℃、酶量4.98 U、双氧水0.1 mmol/L、刚果红20 mg/L，此时刚果红最高降解率为34.84%。然后选双氧水浓度、刚果红浓度和灰盖鬼伞过氧化物酶量作为3个因素，通过中心组合设计实验，用响应面法对刚果红降解进行优化分析，最后得到一个拟合度良好的二次多项方程模型（R²=0.9900）。方差分析结果显示，刚果红浓度和酶量是影响最显著的因素，双氧水与酶以及染料与酶之间的交互作用极显著。响应面分析优化后的反应体系为：双氧水浓度0.15 mmol/L，刚果红浓度为27.21 mg/L，酶为2.0 7 U，在此条件下，刚果红降解率达58.13%。