More than 20 sequences of phospholipid hydroperoxide glutathione peroxidase (PHGPX) from a sequence database were analyzed. The analyses show that the primary structures of most PHGPX proteins have three highly con...More than 20 sequences of phospholipid hydroperoxide glutathione peroxidase (PHGPX) from a sequence database were analyzed. The analyses show that the primary structures of most PHGPX proteins have three highly conserved regions forming a catalytic center and have more than 50% amino acid sequence identity in common. However, two PHGPXs from bovine and swine with the same function have very low similarity with typical PHGPXs and do not have the three highly conserved regions. Thus, the PHGPX proteins are divided into two types: those with the three highly conserved regions, designated as PHGPX I, and the others as PHGPX II. In general, type I proteins are composed of ca.170 amino acid residues; a few of them have an extra signal peptide sequence at the N terminal of the protein. The composition of plant and animal PHGPX amino acids is very different, with most plant PHGPXs being weak acidic, while most animal ones are alkaline. Another specific conservative motif is also found in plant PHGPX proteins. System evolution analysis shows that ortholog and paralog evolution models both exist in PHGPXs, with the plant PHGPX and the animal PHGPX diverging exclusively into two branches in PHGPX I. The information revealed by the evolution tree agrees with the general species evolution process from low to advanced and from simple to complicated. 展开更多
The family of glutathione peroxidases encompasses, as far, three tetrameric glutathione'peroxidases (GPx) and the monomeric PHGPx. Although the overall homology between tetrameric enzymes and PHGPx is less than 30...The family of glutathione peroxidases encompasses, as far, three tetrameric glutathione'peroxidases (GPx) and the monomeric PHGPx. Although the overall homology between tetrameric enzymes and PHGPx is less than 30%, a pronounced similarity has been detected on clusters involved in the active site and a common catalytic triad (selenocysteine glutamine and tryptophan) has been defined by structural and kinetic data.A major peculiar feature of the reaction catalyzed by PHGPx is the possibility to accommodate large lipophilic substrates. This accounts for the observed dramatic antiperoxidant effect and the synergism with vitamin E.Moreover, the reduction of lipid hydroperoxides accounts also for the observed modulation of cycloxygenase and inhibition of 15-lipoxygenase.On the other hand, structural and kinetic data indicate that also the specificity of PHGPx for the donor substrate is not restricted to GSH and the recent observation the PHGPx binds to specific mitochondrial proteins, from which it is released by ionic strength and thiols, suggests a possible fole of this seleooenzyme'in catalyzing the specific oxidation of protein thiols,thus modulating the activity of cellular regulatory elements. on this light, the selenium mojety of PHGPx, reacting much faster that thiols with a peroxide, and then oxidizing specific protein thiols, would channel the oxidation toward protein targets, thus providing, by protein-protein interaction, the specificity of the redox transition展开更多
Selenoprotein biosynthesis may not only be affected by the availability of selenium and the transcription rate of pertinent genes but also by the activity of components of the selenocysteine incorporation complex, Sel...Selenoprotein biosynthesis may not only be affected by the availability of selenium and the transcription rate of pertinent genes but also by the activity of components of the selenocysteine incorporation complex, SelA, B, C, or D. Incorporation of selenocysteine into selenoproteins requires a complex co-translational mechanism guaranteeing the correct recoding of the termination codon TGA as selenocysteine codon. A particular tRNASer(Sec) is enzyrnatically transformed by selenophosphate into tRNAsec which recognizes the UGA codon by means of a specific elongation factor (SelB) and a peculiar mRNA secondary structure. Selenophosphate is formed from selenide and ATP by the SelD gene product, selenophosphate synthase (SelD). To further elucidate the biological role of phospholipid hydroperoxide GPx (PHGPx), we transformed cells with a heterologous (pig) PHGPx gene and/or an additional (human) SelD gene and studied the behaviour of these cells under selenium depletion and repletion. Transfection of the endothelial cell line ECV 304 with either PHGPx cDNA or SelD cDNA did not result in a substantial increase of PHGPx activities, independent of selenium supply. However, cells co-trans fected with both, PHGPx and SelD cDNA, expressed significantly higher PHGPx activlty. This effect was much more pronounced under selenium limiting conditions. The enhanced PHGPx activity correlated with two functional pararneters, increased capability to reduce hydroperoxides and less sensitivity against H2O2-induced cytotoxicity. Thus, the ECV cells, stably transfected with PHGPx and SelD cDNA, provide a model to specifically investigate the role of PHGPx in endothelial cell function展开更多
Objective:To investigate if the protective effect ofα-tocopherol against the impact of ethanol on brain morphogenesis involved the activity of the selenoproteins phospholipid hydroperoxide glutathione peroxidase (PHG...Objective:To investigate if the protective effect ofα-tocopherol against the impact of ethanol on brain morphogenesis involved the activity of the selenoproteins phospholipid hydroperoxide glutathione peroxidase (PHGPx;GPx4) and selenoprotein P (SelPP) that have roles against oxidative stress.Methods:Forty female mice were randomly assigned into natural control (CON), positive control (ETOH), low-, medium-, and high-α-tocopherol-supplemented-ethanol groups (LTOC, MTOC, HTOC, respectively). CON received drinking water without ethanol while ETOH, LTOC, MTOC and HTOC groups received 20% ethanol in drinking water. The supplemented groups were given respective dosages ofα-tocopherol, 0.410, 0.819, and 1.640 mg/g body weight, at day 14 before mating onwards to the day 9 of gestation. At 10.5 ED of gestation (1100 h), the pregnant females were sacrificed by cervical dislocation and the embryos were harvested. Total RNA were extracted, cDNA synthesis and qRT- PCR analyses were carried out.Results: The level of expression of PHGPx in the positive control was significantly lower than that of the natural control. Among the threeα-tocopherol-supplemented groups, only the medium dose- group was significantly higher than the positive control. The level of expression of SelPP in the positive control was significantly lower than those of the natural control, the low- and medium- dose -tocopherol supplemented groups. In the high dose-α-tocopherol supplemented group, the level of expression was not significantly different from the positive control but significantly lower than the natural control.Conclusions: The activity of the selenoproteins PHGPx and SelPP are involved in the internetwork of antioxidative enzymes with vitamin E when given up to a medium dose only and is one of the possible pathways of shielding embryonic development against the impact of ethanol on brain morphogenesis. This study strengthens the impact of dietaryα-tocopherol and Selenium supplement during the critical period of pregnancy.展开更多
Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is a unique antioxidative enzyme which specifically catalyses the reduction of phospholipid hydroperoxides so as to protect biomembrane from oxidative injury. ...Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is a unique antioxidative enzyme which specifically catalyses the reduction of phospholipid hydroperoxides so as to protect biomembrane from oxidative injury. A radish cDNA encoding putative PHGPx (RsPHGPx, GenBank accession number AF322903) was展开更多
In the blood fluke Schistosoma mansoni a functionally active, monomeric, phospholipid hydroperoxide glutathione peroxidase (PHGPx) has been purified and characterized. This enzyme contains a catalytically active selen...In the blood fluke Schistosoma mansoni a functionally active, monomeric, phospholipid hydroperoxide glutathione peroxidase (PHGPx) has been purified and characterized. This enzyme contains a catalytically active selenocysteine. The protein has been shown to be the product of a cloned gene, previously referred to as a glutathione peroxidase gene. S. mansoni PHGPx has been found 5 times more abundant in female than in male worm extract. As in vertebrate PHGPx, homology alignment indicates that the residues involved in the glutathione binding by the tetrameric cellular glutathione peroxidase are mutated in the S. mansoni enzyme. Thus, this aspect appears a landmark of the PHGPx-type of glutathione peroxidases,which might be of functional relevance展开更多
基金supported by grants from the Hi-Tech Research and Development Program of China (2007AA100604)The National Natural Science Foundation of China (30170080, 39770078)+1 种基金National Basic Research Program of China (2006CB101706)Tsinghua-Yu-Yuan Medical Sciences Fund~~
基金Supported by the National Natural Science F oundationof China(Nos. 3 9770 0 78and 3 0 170 0 80 )the NationalTransgenic Plant Research Project(No.J99-A-041)+1 种基金State Key Basic Research and Development Plan(No.G199980 10 10 0 )Yunnan Province-Unive
文摘More than 20 sequences of phospholipid hydroperoxide glutathione peroxidase (PHGPX) from a sequence database were analyzed. The analyses show that the primary structures of most PHGPX proteins have three highly conserved regions forming a catalytic center and have more than 50% amino acid sequence identity in common. However, two PHGPXs from bovine and swine with the same function have very low similarity with typical PHGPXs and do not have the three highly conserved regions. Thus, the PHGPX proteins are divided into two types: those with the three highly conserved regions, designated as PHGPX I, and the others as PHGPX II. In general, type I proteins are composed of ca.170 amino acid residues; a few of them have an extra signal peptide sequence at the N terminal of the protein. The composition of plant and animal PHGPX amino acids is very different, with most plant PHGPXs being weak acidic, while most animal ones are alkaline. Another specific conservative motif is also found in plant PHGPX proteins. System evolution analysis shows that ortholog and paralog evolution models both exist in PHGPXs, with the plant PHGPX and the animal PHGPX diverging exclusively into two branches in PHGPX I. The information revealed by the evolution tree agrees with the general species evolution process from low to advanced and from simple to complicated.
文摘The family of glutathione peroxidases encompasses, as far, three tetrameric glutathione'peroxidases (GPx) and the monomeric PHGPx. Although the overall homology between tetrameric enzymes and PHGPx is less than 30%, a pronounced similarity has been detected on clusters involved in the active site and a common catalytic triad (selenocysteine glutamine and tryptophan) has been defined by structural and kinetic data.A major peculiar feature of the reaction catalyzed by PHGPx is the possibility to accommodate large lipophilic substrates. This accounts for the observed dramatic antiperoxidant effect and the synergism with vitamin E.Moreover, the reduction of lipid hydroperoxides accounts also for the observed modulation of cycloxygenase and inhibition of 15-lipoxygenase.On the other hand, structural and kinetic data indicate that also the specificity of PHGPx for the donor substrate is not restricted to GSH and the recent observation the PHGPx binds to specific mitochondrial proteins, from which it is released by ionic strength and thiols, suggests a possible fole of this seleooenzyme'in catalyzing the specific oxidation of protein thiols,thus modulating the activity of cellular regulatory elements. on this light, the selenium mojety of PHGPx, reacting much faster that thiols with a peroxide, and then oxidizing specific protein thiols, would channel the oxidation toward protein targets, thus providing, by protein-protein interaction, the specificity of the redox transition
文摘Selenoprotein biosynthesis may not only be affected by the availability of selenium and the transcription rate of pertinent genes but also by the activity of components of the selenocysteine incorporation complex, SelA, B, C, or D. Incorporation of selenocysteine into selenoproteins requires a complex co-translational mechanism guaranteeing the correct recoding of the termination codon TGA as selenocysteine codon. A particular tRNASer(Sec) is enzyrnatically transformed by selenophosphate into tRNAsec which recognizes the UGA codon by means of a specific elongation factor (SelB) and a peculiar mRNA secondary structure. Selenophosphate is formed from selenide and ATP by the SelD gene product, selenophosphate synthase (SelD). To further elucidate the biological role of phospholipid hydroperoxide GPx (PHGPx), we transformed cells with a heterologous (pig) PHGPx gene and/or an additional (human) SelD gene and studied the behaviour of these cells under selenium depletion and repletion. Transfection of the endothelial cell line ECV 304 with either PHGPx cDNA or SelD cDNA did not result in a substantial increase of PHGPx activities, independent of selenium supply. However, cells co-trans fected with both, PHGPx and SelD cDNA, expressed significantly higher PHGPx activlty. This effect was much more pronounced under selenium limiting conditions. The enhanced PHGPx activity correlated with two functional pararneters, increased capability to reduce hydroperoxides and less sensitivity against H2O2-induced cytotoxicity. Thus, the ECV cells, stably transfected with PHGPx and SelD cDNA, provide a model to specifically investigate the role of PHGPx in endothelial cell function
基金De La Sale University-University Research Coordination OficeUniversity Science Foundation(USF)under project#43FU/S309 and partly from the Department of Science and Technology.
文摘Objective:To investigate if the protective effect ofα-tocopherol against the impact of ethanol on brain morphogenesis involved the activity of the selenoproteins phospholipid hydroperoxide glutathione peroxidase (PHGPx;GPx4) and selenoprotein P (SelPP) that have roles against oxidative stress.Methods:Forty female mice were randomly assigned into natural control (CON), positive control (ETOH), low-, medium-, and high-α-tocopherol-supplemented-ethanol groups (LTOC, MTOC, HTOC, respectively). CON received drinking water without ethanol while ETOH, LTOC, MTOC and HTOC groups received 20% ethanol in drinking water. The supplemented groups were given respective dosages ofα-tocopherol, 0.410, 0.819, and 1.640 mg/g body weight, at day 14 before mating onwards to the day 9 of gestation. At 10.5 ED of gestation (1100 h), the pregnant females were sacrificed by cervical dislocation and the embryos were harvested. Total RNA were extracted, cDNA synthesis and qRT- PCR analyses were carried out.Results: The level of expression of PHGPx in the positive control was significantly lower than that of the natural control. Among the threeα-tocopherol-supplemented groups, only the medium dose- group was significantly higher than the positive control. The level of expression of SelPP in the positive control was significantly lower than those of the natural control, the low- and medium- dose -tocopherol supplemented groups. In the high dose-α-tocopherol supplemented group, the level of expression was not significantly different from the positive control but significantly lower than the natural control.Conclusions: The activity of the selenoproteins PHGPx and SelPP are involved in the internetwork of antioxidative enzymes with vitamin E when given up to a medium dose only and is one of the possible pathways of shielding embryonic development against the impact of ethanol on brain morphogenesis. This study strengthens the impact of dietaryα-tocopherol and Selenium supplement during the critical period of pregnancy.
文摘Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is a unique antioxidative enzyme which specifically catalyses the reduction of phospholipid hydroperoxides so as to protect biomembrane from oxidative injury. A radish cDNA encoding putative PHGPx (RsPHGPx, GenBank accession number AF322903) was
文摘In the blood fluke Schistosoma mansoni a functionally active, monomeric, phospholipid hydroperoxide glutathione peroxidase (PHGPx) has been purified and characterized. This enzyme contains a catalytically active selenocysteine. The protein has been shown to be the product of a cloned gene, previously referred to as a glutathione peroxidase gene. S. mansoni PHGPx has been found 5 times more abundant in female than in male worm extract. As in vertebrate PHGPx, homology alignment indicates that the residues involved in the glutathione binding by the tetrameric cellular glutathione peroxidase are mutated in the S. mansoni enzyme. Thus, this aspect appears a landmark of the PHGPx-type of glutathione peroxidases,which might be of functional relevance
