The Experts below are selected from a list of 101973 Experts worldwide ranked by ideXlab platform
Aron B Fisher - One of the best experts on this subject based on the ideXlab platform.
-
peroxiredoxin 6 in the repair of peroxidized cell membranes and cell signaling
Archives of Biochemistry and Biophysics, 2017Co-Authors: Aron B FisherAbstract:Peroxiredoxin 6 represents a widely distributed Group of peroxiredoxins that contain a single conserved cysteine in the protein monomer (1-cys Prdx). The cys when oxidized to the sulfenic form is reduced with glutathione (GSH) catalyzed by the π isoform of GSH-S-transferase. Three enzymatic activities of the protein have been described:1) peroxidase with H2O2, short chain hydroperoxides, and phospholipid hydroperoxides as substrates; 2) phospholipase A2 (PLA2); and 3) lysophosphatidylcholine acyl transferase (LPCAT). These activities have important physiological roles in antioxidant defense, turnover of cellular phospholipids, and the generation of superoxide anion via initiation of the signaling cascade for activation of NADPH oxidase (type 2). The ability of Prdx6 to reduce peroxidized cell membrane phospholipids (peroxidase activity) and also to replace the oxidized sn-2 fatty acyl Group through hydrolysis/reacylation (PLA2 and LPCAT activities) provides a complete system for the repair of peroxidized cell membranes.
-
peroxiredoxin 6 a bifunctional enzyme with glutathione peroxidase and phospholipase a activities
Antioxidants & Redox Signaling, 2011Co-Authors: Aron B FisherAbstract:Peroxiredoxin 6 (Prdx6) is the prototype and the only mammalian 1-Cys member of the Prdx family. Major differences from 2-Cys Prdxs include the use of glutathione (GSH) instead of thioredoxin as the physiological reductant, heterodimerization with πGSH S-transferase as part of the catalytic cycle, and the ability either to reduce the oxidized sn-2 fatty acyl Group of phospholipids (peroxidase activity) or to hydrolyze the sn-2 ester (alkyl) bond of phospholipids (phospholipase A2 [PLA2] activity). The bifunctional protein has separate active sites for peroxidase (C47, R132, H39) and PLA2 (S32, D140, H26) activities. These activities are dependent on binding of the protein to phospholipids at acidic pH and to oxidized phospholipids at cytosolic pH. Prdx6 can be phosphorylated by MAP kinases at T177, which markedly increases its PLA2 activity and broadens its pH-activity spectrum. Prdx6 is primarily cytosolic but also is targeted to acidic organelles (lysosomes, lamellar bodies) by a specific targeting sequence (amino acids 31–40). Oxidant stress and keratinocyte growth factor are potent regulators of Prdx6 gene expression. Prdx6 has important roles in both antioxidant defense based on its ability to reduce peroxidized membrane phospholipids and in phospholipid homeostasis based on its ability to generate lysophospholipid substrate for the remodeling pathway of phospholipid synthesis. Antioxid. Redox Signal. 15, 831–844.
-
Peroxiredoxin 6: a bifunctional enzyme with glutathione peroxidase and phospholipase A₂ activities.
Antioxidants & Redox Signaling, 2011Co-Authors: Aron B FisherAbstract:Peroxiredoxin 6 (Prdx6) is the prototype and the only mammalian 1-Cys member of the Prdx family. Major differences from 2-Cys Prdxs include the use of glutathione (GSH) instead of thioredoxin as the physiological reductant, heterodimerization with πGSH S-transferase as part of the catalytic cycle, and the ability either to reduce the oxidized sn-2 fatty acyl Group of phospholipids (peroxidase activity) or to hydrolyze the sn-2 ester (alkyl) bond of phospholipids (phospholipase A2 [PLA2] activity). The bifunctional protein has separate active sites for peroxidase (C47, R132, H39) and PLA2 (S32, D140, H26) activities. These activities are dependent on binding of the protein to phospholipids at acidic pH and to oxidized phospholipids at cytosolic pH. Prdx6 can be phosphorylated by MAP kinases at T177, which markedly increases its PLA2 activity and broadens its pH-activity spectrum. Prdx6 is primarily cytosolic but also is targeted to acidic organelles (lysosomes, lamellar bodies) by a specific targeting sequence (amino acids 31–40). Oxidant stress and keratinocyte growth factor are potent regulators of Prdx6 gene expression. Prdx6 has important roles in both antioxidant defense based on its ability to reduce peroxidized membrane phospholipids and in phospholipid homeostasis based on its ability to generate lysophospholipid substrate for the remodeling pathway of phospholipid synthesis. Antioxid. Redox Signal. 15, 831–844.
Ernst Heinz - One of the best experts on this subject based on the ideXlab platform.
-
biosynthesis of docosahexaenoic acid in euglena gracilis biochemical and molecular evidence for the involvement of a delta4 fatty acyl Group desaturase
Biochemistry, 2003Co-Authors: Astrid Meyer, Petra Cirpus, Rainer Schlecker, Ulrich Zahringer, Claudia Ott, Ernst HeinzAbstract:Docosahexaenoic acid (DHA) can be synthesized via alternative routes from which only the ω3/ω6-pathways involve the action of a Δ4-fatty acid desaturase. We examined the suitability of Euglena gracilis, Thraustochytrium sp., Schizochytrium sp., and Crypthecodinium cohnii to serve as sources for cloning a cDNA encoding a Δ4-fatty acid desaturase. For this purpose we carried out in vivo labeling studies with radiolabeled C22 polyunsaturated fatty acid substrates. Schizochytrium sp. was unable to convert exogenously supplied [2-14C]-docosapentaenoic acid (DPA, 22:5Δ7,10,13,16,19) to DHA, while E. gracilis and Thraustochytrium sp. carried out this desaturation very efficiently. Hydrogenation and α-oxidation of the labeled DHA isolated from these two organisms showed that it was the result of direct Δ4-desaturation and not of substrate breakdown and resynthesis. To clone the desaturase gene, a cDNA library of E. gracilis was subjected to mass sequencing. A full-length clone with highest homology to the Δ4-desa...
-
biosynthesis of docosahexaenoic acid in euglena gracilis biochemical and molecular evidence for the involvement of a δ4 fatty acyl Group desaturase
Biochemistry, 2003Co-Authors: Astrid Meyer, Petra Cirpus, Rainer Schlecker, Ulrich Zahringer, Ernst HeinzAbstract:Docosahexaenoic acid (DHA) can be synthesized via alternative routes from which only the ω3/ω6-pathways involve the action of a Δ4-fatty acid desaturase. We examined the suitability of Euglena gracilis, Thraustochytrium sp., Schizochytrium sp., and Crypthecodinium cohnii to serve as sources for cloning a cDNA encoding a Δ4-fatty acid desaturase. For this purpose we carried out in vivo labeling studies with radiolabeled C22 polyunsaturated fatty acid substrates. Schizochytrium sp. was unable to convert exogenously supplied [2-14C]-docosapentaenoic acid (DPA, 22:5Δ7,10,13,16,19) to DHA, while E. gracilis and Thraustochytrium sp. carried out this desaturation very efficiently. Hydrogenation and α-oxidation of the labeled DHA isolated from these two organisms showed that it was the result of direct Δ4-desaturation and not of substrate breakdown and resynthesis. To clone the desaturase gene, a cDNA library of E. gracilis was subjected to mass sequencing. A full-length clone with highest homology to the Δ4-desa...
Jong Shin Yoo - One of the best experts on this subject based on the ideXlab platform.
-
Tandem mass spectrometric analysis of fatty acyl Groups of galactolipid molecular species from wheat flour
Microchemical Journal, 2001Co-Authors: Young Hwan Kim, Ji Hye Gil, Jongki Hong, Jong Shin YooAbstract:Our previous work demonstrated that the structures of two and one molecular species of digalactosyl and monogalactosyl diacylglycerols from wheat flour, respectively, were determined by collision-induced dissociation (CID) of sodium-adducted molecules ([M+Na]+) desorbed by fast atom bombardment (FAB). However, many more components in their HPLC separations were identified. Then fractionated components were structurally determined by CID tandem mass spectrometry (MS/MS), including the fatty acid composition and the double-bond positions in the fatty acyl Groups. Furthermore, the relative positions of two fatty acid chains on the glycerol backbone could be assigned by the ratio of the intensity of two specific product ions observed in the CID spectra. The product ion ([M+Na-R2COOH]+) due to the neutral loss of the fatty acyl Group at the sn-2 position via free fatty acid was more abundant than the one ([M+Na-R1COOH]+) due to the loss of the fatty acyl Group at the sn-1 position. The regiospecificity of two fatty acyl linkages was also confirmed by the results which were obtained from the FAB mass spectra of sn-2 acyl lysogalactolipids. These compounds were synthesized by a specific enzyme, Lipase XI (from Rhizopus arrhizus), which cleaved specifically ester bond between glycerol backbone and sn-1 fatty acyl Group.
Colin Hughes - One of the best experts on this subject based on the ideXlab platform.
-
an ordered reaction mechanism for bacterial toxin acylation by the specialized acyltransferase hlyc formation of a ternary complex with acylacp and protoxin substrates
Molecular Microbiology, 1999Co-Authors: Peter Stanley, Vassilis Koronakis, Caroline Hyland, Colin HughesAbstract:: The 110 kDa haemolysin protoxin (proHlyA) is activated in the Escherichia coli cytosol by acyl carrier protein-dependent fatty acylation of two internal lysine residues, directed by the co-synthesized protein HlyC. Using an in vitro maturation reaction containing purified protoxin peptides and acylACP, we show unambiguously that HlyC possesses an apparently unique acyltransferase activity fully described by Michaelis-Menten analysis. The Vmax of HlyC at saturating levels of both substrates was approximately 115 nmol acyl Group min-1 mg-1 with KMacylACP of 260 nM and KMproHlyA of 27 nM, kinetic parameters sufficient to explain why in vivo HlyC is required at a concentration equimolar to proHlyA. HlyC bound the fatty acyl Group from acylACP to generate an acylated HlyC intermediate that was depleted in the presence of proHlyA, but enriched in the presence of proHlyA derivatives lacking acylation target sites. HlyC was also able to bind in vivo 4'-phosphopantetheine. Substitution of conserved amino acids that could act as putative covalent attachment sites did not prevent binding of the fatty acyl or 4'-phosphopantetheine Groups. These data and substrate variation analyses suggest that the unique acylation reaction does not involve covalent attachment of fatty acid to the acyltransferase, but rather that it proceeds via a sequential ordered Bi-Bi reaction mechanism, requiring the formation of a non-covalent ternary acylACP-HlyC-proHlyA complex.
-
Activation of Escherichia coli prohaemolysin to the mature toxin by acyl carrier protein-dependent fatty acylation.
Nature, 1991Co-Authors: Jean-paul Issartel, Vassilis Koronakis, Colin HughesAbstract:HAEMOLYSIN secreted by pathogenic Escherichia coli binds to mammalian cell membranes, disrupting cellular activities and lysing cells by pore-formation. It is synthesized as nontoxic prohaemolysin (proHlyA), which is activated intracellularly by a mechanism dependent on the cosynthesized HlyC. Haemolysin is one of a family of membrane-targeted toxins, including the leukotoxins of Pasteurella and Actinobacillus and the bifunctional adenylate cyclase haemolysin of Bordetella pertussis, which require this protoxin activation1–5. HlyC alone cannot activate proHlyA, but requires a cytosolic activating factor6. Here we report the cytosolic activating factor is identical to the acyl carrier protein and that activation to mature toxin is achieved by the transfer of a fatty acyl Group from acyl carrier protein to proHlyA. Only acyl carrier protein, not acyl-CoA, can promote HlyC-directed proHlyA acylation, but a range of acyl Groups are effective.
Akira Tokumura - One of the best experts on this subject based on the ideXlab platform.
-
Altered phospholipid profile in urine of rats with unilateral ureteral obstruction
Metabolomics, 2009Co-Authors: Yasuko Yoshioka, Toshihiko Tsutsumi, Mika Adachi, Akira TokumuraAbstract:Little is known about renal damage to the contralateral kidney after unilateral ureteral obstruction (UUO). Using liquid chromatography-time of flight-mass spectrometry combined with principal component analysis (PCA), we compared urinary phospholipid profiles before and two weeks after UUO in rats. PCA revealed that negative ions corresponding to three molecular species of phosphatidylethanolamine (PE) and two species of phosphatidylglycerol (PG) had a higher score than other phospholipids such as phosphatidylcholine, phosphatidylinositol, and sphingomyelin. The assigned species of PE and PG were postulated to possess a monoenoic or dienoic fatty acyl Group, and the ratios of their levels in urine from UUO to that in the controls were much higher than those having a highly polyunsaturated fatty acyl Group. These results indicate that PE and PG having a monoenoic or dienoic fatty acyl Group are potential biomarkers for injury of contralateral kidney after UUO.
-
Human platelets respond differentially to lysophosphatidic acids having a highly unsaturated fatty acyl Group and alkyl ether-linked lysophosphatidic acids.
The Biochemical journal, 2002Co-Authors: Akira Tokumura, Junya Sinomiya, Seishi Kishimoto, Tamotsu Tanaka, Kentaro Kogure, Takayuki Sugiura, Kiyoshi Satouchi, Keizo Waku, Kenji FukuzawaAbstract:Lysophosphatidic acid (LPA) is a physiological agonist that is produced by lysophospholipase D, phospholipase A(1) and phospholipase A(2) in the blood of animals. It exerts diverse biological actions on a broad range of animal cells. Specific receptors for this important agonist have been characterized. In this investigation, for the first time we prepared LPAs having a highly unsaturated fatty acyl Group, such as the eicosapentaenoyl or docosahexaenoyl residue, and their acetylated derivatives. Human platelets aggregated more potently in response to the highly unsaturated acyl-LPAs than to LPAs with a C(18) fatty acyl Group, such as an oleoyl Group, while alkyl ether-linked LPAs (alkyl-LPA) had much stronger aggregating activity. Two positional isomers of LPAs with an arachidonoyl, eicosapentaenoyl or docosahexaenoyl Group had equipotent aggregatory activity as well as the positional isomers of their acetylated analogues, indicating that putative LPA receptors could not distinguish the difference between the positional isomers. We found that platelet preparations from two individuals showed no aggregatory response to alkyl-LPAs, although they contained mRNAs for known LPA receptors in the following order of expression level: endothelial differentiation gene (Edg)-4>Edg-7>Edg-2. We also obtained evidence that 2-(p-amylcinnamoyl)amino-4-chlorobenzoic acid (ONO-RS-082), a phospholipase A(2) inhibitor, potentiated alkyl-LPA-induced platelet aggregation, but inhibited highly unsaturated acyl-LPA-induced platelet aggregation. These results indicated that human platelets express acyl-LPA-selective and alkyl-LPA-selective receptors on their plasma membrane.
