Danny T.Y. Chiu
Bio: Danny T.Y. Chiu is an academic researcher from University of California, Davis. The author has contributed to research in topics: Glutathione peroxidase & GPX6. The author has an hindex of 3, co-authored 3 publications receiving 414 citations.
TL;DR: The kinetic behavior or the purified lung soluble gluthathione peroxidase followed a ping-pong-like mechanism; the enzyme first reduced the lipid hydroperoxide substrate to the corresponding hydroxy fatty acid, then was regenerated to the native form by reduced glutathione.
TL;DR: The glutathione peroxidase enzyme was isolated as a neutrally charged protein and became negatively charged upon storage, a phenomenon that was independent of the aggregation.
TL;DR: Purified rat liver soluble glutathione peroxidase, with a specific activity of 280 μmol of NADPH oxidized/min/mg of protein, was studied by X-ray photoelectron spectroscopy and found selenium 3d electron signals observed gave evidence that seenium in glutATHione per oxidase is not bound to oxygen.
TL;DR: In this article, the authors reviewed the mitochondrial rates of production and steady state levels of reactive oxygen species generated by mitochondria, or from other sites within or outside the cell, cause damage to mitochondrial components and initiate degradative processes.
TL;DR: The procedure presented in this work can easily be applied to other cell lines and provides a quantitative framework to interpret the data obtained when cells are exposed to an external source of H2O2.
TL;DR: The aggregation studies suggest that the in vivo form of the enzyme may be a large aggregate, and the hypothesis that glutathione peroxidase protects membranes from damage due to lipid peroxidation requires that the soluble enzyme come in contact with the peroxide substrates in the membrane.
Abstract: Publisher Summary Gluthatione peroxidase is assayed by a modification of the method of Paglia and Valentine. Glutathione peroxidase catalyzes the reduction of hydroperoxides with glutathione as the reductant. The simple method is a spectrophotometric assay in which the reduction of GSSG is coupled to the oxidation of NADPH through glutathione reductase. The acetone precipitation serves to partially purify as well as concentrate the sample for application onto chromatography columns. The multiplicity of forms of glutathione peroxidase in vitro may or may not represent true in vivo forms. The hypothesis that glutathione peroxidase protects membranes from damage due to lipid peroxidation requires that the soluble enzyme come in contact with the peroxide substrates in the membrane. Study of the multiple forms may give information about the characteristics of the enzyme and the role it plays in protecting the cell from peroxidative damage. The aggregation studies suggest that the in vivo form of the enzyme may be a large aggregate. The enzyme resists disaggregation by the normal agents used for this purpose.
TL;DR: It was concluded that the reduced form of glutathione peroxidase contains the selenocysteine selenol (-SeH) at the catalytic site.
Abstract: A procedure was developed to isolate 75Se-labeled rat liver glutathione peroxidase (glutathione:H2O2 oxidoreductase, EC 188.8.131.52) at 30--50% purity with 20--30% yields in 4--5 days. Using these preparations of glutathione peroxidase, the selenium moiety in the enzyme was identified as selenocysteine by derivatizing the seleno group with either iodoacetate or ethylenimine in the intact protein, hydrolyzing the protein with 6 N HCl, and cochromatographing the 75Se-labeled products with known standards. Techniques employed were anion-exchange chromatography, cation-exchange chromatography, gel-permeation chromatography, two-dimensional thin-layer chromatography, and automated amino acid analysis. The selenocysteine moiety was identified as the catalytic site in glutathione peroxidase by specifically labeling the enzyme with [14C]iodoacetate on the 75Se-labeled selenium atom and fractionating the 14C, 75Se-labeled derivative after acid hydrolysis. It was concluded that the reduced form of glutathione peroxidase contains the selenocysteine selenol (-SeH) at the catalytic site.
TL;DR: High fat diet-induced obesity is accompanied by increased hepatic, heart, and renal tissues oxidative stress, which is characterized by reduction in the antioxidant enzymes activities and glutathione levels, that correlate with the increase in MDA and PCO levels in most tissues.
Abstract: Background: Obesity has become a leading global health problem owing to its strong association with a high incidence of diseases. Aim: To induce rat obesity using high fat diet (HFD) and to estimate oxidative stress markers in their liver, heart and kidney tissues in order to shed the light on the effect of obesity on these organs. Materials and methods: Sixty white albino rats weighing 150-200 g were randomly divided into two equal groups; group I: received high fat diet for 16 weeks, and group II (control group): received only normal diet (rat chow) for 16 weeks. Blood samples were taken for measurement of lipid profile, tissue samples from liver, heart and kidney were taken for determination of malondialdehyde (MDA), protein carbonyl (PCO), reduced glutathione (GSH) levels, and the activities of glutathione S- transferase (GST) glutathione peroxidase (GPx), catalase (CAT) and paraoxonase1 (PON1) enzymes. Results: Data showed that feeding HFD diet significantly increased final body weight and induced a state of dyslipideamia. Also our results showed a significant increase MDA and PCO levels in the hepatic, heart and renal tissues of obese rats, as well as a significant decrease in the activity of GST, GPx and PON 1 enzymes. On the other hand CAT enzyme activity showed significant decrease only in renal tissues of obese rats with non significant difference in hepatic and heart tissues. GSH levels showed significant decrease in both renal and hepatic tissues of obese animals and significant increase in their heart tissues. Correlation studies in obese animals showed a negative correlation between MDA and PCO tissue levels and the activities of GPx, GST and PON1 in all tissues and also with CAT enzyme activity in renal tissues. Also a negative correlation was detected between MDA & PCO tissues levels and GSH levels in both hepatic and renal tissues. While positive correlation was found between them and GSH levels in heart tissues. Conclusion: High fat diet-induced obesity is accompanied by increased hepatic, heart, and renal tissues oxidative stress, which is characterized by reduction in the antioxidant enzymes activities and glutathione levels, that correlate with the increase in MDA and PCO levels in most tissues. This may probably contribute to the additional progression of obesity related problems.