Theoretical Study on GSH Activation Mechanism of a New Type of Glutathione Transferase Gtt2

Glutathione transferases（GSTs） play an important role in the detoxification of xenobiotic/endobiotic toxic compounds. The α-, π-, and/l-classes of cytosolic GSTs have been studied extensively, while Gtt2 from Saccharo- myces cerevisiae, a novel atypical GST, is still poorly understood. In the present study, we investigated the gluta- thione（GSH） activation mechanism of Gtt2 using the density functional theory（DFT） with the hybrid functional B3LYP. The computational results show that a water molecule could assist a proton transfer between the GSH thiol and the N atom of His133. The energy barrier of proton transfer is 46.0 kJ/mol. The GSH activation mechanism and the characteristics of active site are different from those of classic cytosolic GSTs.

Effects of PAHs on Biotransformation Enzymatic Activities in Fish

Biotransformation and detoxification responses to the exposure to five polycyclic aromatic hydrocarbons were investigated in crucian（Carassius auratus）. Juvenile crucian were treated with a single intraperitoneal injection of each compound at dosages of 0.1, 1.0, 2.0, 5.0 and 8.0（or 10.0） mg/kg and sacrificed 15 d later to determine 7-ethoxyresorufin-O-deethylase（EROD） and glutathione S-transferases（GST） activities in gill S9 fractions. EROD activity is significantly increased by benzo（b）fluoranthene and indeno（1,2,3-cd）pyrene at all the doses. High dosages of PAHs induced GST activity and the inducing ability of them increased in the following order： fluorene fluorantheneindeno（1,2,3-cd）pyrenebenzo（g,h,i）perylenebenzo（b）fluoranthene. In all the cases, dose dependence appeared to exist. The gill EROD and GST in Carassius auratus are useful biomarkers to estimate sub-acute toxicity of both polycyclic aromatic hydrocarbons（PAHs） and PAHs-like compounds.

Effects of Different Cadmium Levels on Active Oxygen Metabolism and H_2O_2-Scavenging System in Brassica campestris L.ssp.chinensis

The effects of different Cd (Cadmium) levels on generation of active oxygen speceies(AOS) and H2O2-scavenging system in the leaves of Brassica campestris L. ssp. chinensiswere studied. The results showed that generation rate, and H2O2 content were enhancedand malondialdehyde (MDA) content increased with the increase of Cd concentrations inthe growth medium. The activities of ascorbate peroxidase (APX), dehydroascorbatereductase (DR) and glutathione reductase (GR) were promoted by the addition of Cd.Exposed to Cd also increased the contents of ascorbate (AsA) and glutathione (GSH) in theleaves.

Turning carbon dots into selenium bearing nanoplatforms with in vitro GPx-like activity and pro-oxidant activity

Selenium(Se)has been defined as the“Janus element”,with one face showing antioxidant activity and the other pro-oxidant activity.The biological effect of Se depends on both dose and speciation.Se nanoparticles are attracting major interest,although their large-scale preparation for biomedical applications is not trivial.We hypothesize that acid anhydride-coated carbon dots(AACD)are an attractive platform for preparing nanoparticles containing chemically defined Se.The reaction of AA-CD with 3-selenocyanatopropan-1-amine yields carbon dots bearing selenocyanate and carboxylate groups(CD-SeCN)that allow for tuning the hydrosolubility.CD-SeCN has a Se content of 0.36μmol per mg of nanoparticles,they show the typical photoluminescence of carbon dots.The selenocyanate groups(SeCN)exhibited glutathione peroxidase-like activity and cytotoxicity.Data show that antioxidant behavior differs between normal and tumor cells,the evaluation on HEK293 and A549 cells reveals that the toxicity of CD-SeCN depends on dose,time,intracellular glutathione(GSH)content.The toxicity of CD-SeCN decreases with the time of incubation and the cell death mechanism switches from necrosis to apoptosis,indicating that CD-SeCN is neutralized.Additionally,high levels of intracellular GSH exert a protective effect.These results support a pharmacological potential in cancers with low levels of intracellular GSH.The use of AA-CD as nanoplatforms is a general strategy that paves the way for the engineering of advanced nanosystems.