scholarly journals Interaction of rat glutathione S-transferases 7-7 and 8-8 with γ-glutamyl- or glycyl-modified glutathione analogues

1989 ◽  
Vol 264 (3) ◽  
pp. 759-764 ◽  
Author(s):  
A E P Adang ◽  
D J Meyer ◽  
J Brussee ◽  
A Van der Gen ◽  
B Ketterer ◽  
...  
Keyword(s):  
Active Sites ◽  
Ethacrynic Acid ◽  
Acceptor Substrate ◽  
Gamma Glutamyl ◽  
Relative Ability ◽  
Glutathione S Transferases ◽  
Better Than

Analogues of GSH in which either the gamma-glutamyl or the glycyl moiety is modified were synthesized and tested as both substrates for and inhibitors of glutathione S-transferases (GSTs) 7-7 and 8-8. Acceptor substrates for GST 7-7 were 1-chloro-2,4-dinitrobenzene (CDNB) and ethacrynic acid (ETA) and for GST 8-8 CDNB, ETA and 4-hydroxynon-trans-2-enal (HNE). The relative ability of each combination of enzyme and GSH analogue to catalyse the conjugation of all acceptor substrates was similar with the exception of the combination of GST 7-7 and gamma-L-Glu-L-Cys-L-Asp, which used CDNB but not ETA as acceptor substrate. In general, GST 7-7 was better than GST 8-8 in utilizing these analogues as substrates, and glycyl analogues were better than gamma-glutamyl analogues as both substrates and inhibitors. These results are compared with those obtained earlier with GSH analogues and GST isoenzymes 1-1, 2-2, 3-3 and 4-4 [Adang, Brussee, Meyer, Coles, Ketterer, van der Gen & Mulder (1988) Biochem. J. 255, 721-724] and the implications with respect to the nature of their active sites are discussed.

Understanding condensation domain selectivity in non-ribosomal peptide biosynthesis: structural characterization of the acceptor bound state

2021 ◽  
Author(s):  
Max Cryle ◽  
Thierry Izore ◽  
Y. T. Ho ◽  
Joe Kaczmarski ◽  
Athina Gavriilidou ◽  
...  
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Peptide Bond ◽  
Bound State ◽  
Modular Assembly ◽  
Central Function ◽  
Acceptor Substrate ◽  
Peptide Synthetases ◽  
Peptide Biosynthesis ◽  
Condensation Domain

Abstract Non-ribosomal peptide synthetases are important enzymes for the assembly of complex peptide natural products. Within these multi-modular assembly lines, condensation domains perform the central function of chain assembly, typically by forming a peptide bond between two peptidyl carrier protein (PCP)-bound substrates. In this work, we report the first structural snapshots of a condensation domain in complex with an aminoacyl-PCP acceptor substrate. These structures allow the identification of a mechanism that controls access of acceptor substrates to the active site in condensation domains. The structures of this previously uncharacterized complex also allow us to demonstrate that condensation domain active sites do not contain a distinct pocket to select the side chain of the acceptor substrate during peptide assembly but that residues within the active site motif can instead serve to tune the selectivity of these central biosynthetic domains.

The effects of hatchery and wild ancestry and experience on the relative ability of steelhead trout fry (Oncorhynchus mykiss) to avoid a benthic predator

1995 ◽  
Vol 52 (11) ◽  
pp. 2476-2482 ◽  
Author(s):  
Barry A. Berejikian
Keyword(s):  
Oncorhynchus Mykiss ◽  
Predator Avoidance ◽  
Laboratory Experiments ◽  
Test Period ◽  
Natural Environments ◽  
Steelhead Trout ◽  
Visual Exposure ◽  
Natural Stream ◽  
Relative Ability ◽  
Better Than

Differences in selection regimes between hatchery and natural environments and environmental stimuli, among other factors, have the potential to cause differences in predator avoidance ability between hatchery and wild steelhead trout fry (Oncorhynchus mykiss). In two separate laboratory experiments, fry raised from eggs of wild Quinault River steelhead trout survived predation by prickly sculpin (Cottus asper) significantly better than size-matched offspring of a locally derived hatchery population, which were reared under similar conditions. Wild fry also survived predation better than hatchery fry in natural stream enclosures over a 3-day test period. Experience, in the form of 50-min visual exposure to sculpin predation on "sacrificial" steelhead trout, improved the ability of fry from both populations to avoid predation by sculpin. Wild-experienced fry were eaten in the fewest number of trials followed by wild-naive, hatchery-experienced, and hatchery-naive fry. The results of this study are consistent with the hypothesis that innate predator avoidance ability has been negatively altered through domestication and that attempts to condition hatchery-reared steelhead to avoid predators may be limited for domesticated populations.

Constructing Ni–Mo2C Nanohybrids Anchoring on Highly Porous Carbon Nanotubes as Efficient Multifunctional Electrocatalysts

NANO ◽  
2020 ◽  
Vol 15 (10) ◽  
pp. 2050135
Author(s):  
Penglun Zheng ◽  
Quanyi Liu ◽  
Xiaoliang Peng ◽  
Laiquan Li ◽  
Jun Yang
Keyword(s):  
Carbon Nanotubes ◽  
Active Sites ◽  
Reduction Reaction ◽  
Annealing Process ◽  
Interfacial Effect ◽  
Ni Nanoparticles ◽  
Novel Strategy ◽  
Highly Porous ◽  
Nonprecious Metal ◽  
Better Than

It is important for regenerative fuel cells, rechargeable metal–air batteries and water splitting to find reasonable designed nonprecious metal catalysts, which have efficient and durable electrocatalytic activities for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In this work, through a simple hydrothermal method and following annealing process, Mo2C and Ni nanoparticles were encapsulated in a nanoporous hierarchical structure of carbon (Ni/Mo2C/C). The ingenious structure delivers several favorable characteristics including abundant active sites resulting from hollow and mesoporous architecture, boosted reaction kinetics from metallic components, sufficient interfacial effect and synergistic effect from intimate integration of Mo2C, Ni and C. The multifunctional Ni/Mo2C/C hybrid electrocatalyst performs excellently for ORR, OER and HER, better than most of the reported electrocatalysts with three functions. A facile and novel strategy was developed to construct the multifunctional catalysts with excellent electrocatalysis behavior.

scholarly journals Purification and properties of glutathione S-transferases from larvae of Wiseana cervinata

1984 ◽  
Vol 217 (1) ◽  
pp. 41-50 ◽  
Author(s):  
A G Clark ◽  
B Drake
Keyword(s):  
Cation Exchange ◽  
Ethacrynic Acid ◽  
Catalytic Properties ◽  
Exchange Chromatography ◽  
Cation Exchange Chromatography ◽  
Purification And Properties ◽  
Different Types ◽  
Glutathione S Transferases ◽  
Physical And Chemical ◽  
Kinetics Of

The glutathione S-transferases from the porina moth, Wiseanna cervinata, were purified by affinity chromatography, cation-exchange chromatography and preparative isoelectrofocusing. The major transferase (IV) was purified to homogeneity by a factor of 530-fold with a yield of 83%. Other transferases present were purified to a smaller degree (approx. 50-fold) to a stage of near-homogeneity. The transferases examined all had Mr values about 45 000-50 000. They appeared to be homodimers of either of two types of subunit, of Mr 22 800 and 24 600. Enzymes consisting of the different types of subunit were not immunologically cross-reactive. The major enzyme fractions separated by cation-exchange chromatography were both active with 1-chloro-2,4-dinitrobenzene, 1,2-dichloro-4-nitrobenzene, ethacrynic acid and iodomethane, but were inactive with 4-nitropyridine N-oxide, 1,2-epoxy-3-(p-nitrophenoxy)propane, bromosulphophthalein and p-nitrobenzyl chloride. The kinetics of the enzyme-catalysed reaction with enzyme IV were non-Michaelean with respect to both substrates. Both products were inhibitory. The results appear to be compatible with a random steady-state mechanism. It is concluded that these enzymes are very similar, in their physical and chemical constitution, in their catalytic properties and in their relationships with each other, to those enzymes that have been isolated from vertebrate organisms.

scholarly journals The role of tyrosine-9 and the C-terminal helix in the catalytic mechanism of Alpha-class glutathione S-transferases

1999 ◽  
Vol 343 (3) ◽  
pp. 525-531 ◽  
Author(s):  
Claire S. ALLARDYCE ◽  
Paul D. MCDONAGH ◽  
Lu-Yun LIAN ◽  
C. Roland WOLF ◽  
Gordon C. K. ROBERTS
Keyword(s):  
Conformational Change ◽  
Catalytic Mechanism ◽  
Ethacrynic Acid ◽  
Marked Decrease ◽  
Wild Type ◽  
Wild Type Enzyme ◽  
Turnover Number ◽  
Hydrophobic Substrate ◽  
Glutathione S Transferases

Glutathione S-transferases (GSTs) play a key role in the metabolism of drugs and xenobiotics. To investigate the catalytic mechanism, substrate binding and catalysis by the wild-type and two mutants of GST A1-1 have been studied. Substitution of the ‘essential’ Tyr9 by phenylalanine leads to a marked decrease in the kcat for 1-chloro-2,4-dinitrobenzene (CDNB), but has no affect on kcat for ethacrynic acid. Similarly, removal of the C-terminal helix by truncation of the enzyme at residue 209 leads to a decrease in kcat for CDNB, but an increase in kcat for ethacrynic acid. The binding of a GSH analogue increases the affinity of the wild-type enzyme for CDNB, and increases the rate of the enzyme-catalysed conjugation of this substrate with the small thiols 2-mercaptoethanol and dithiothreitol. This suggests that GSH binding produces a conformational change which is transmitted to the binding site for the hydrophobic substrate, where it alters both the affinity for the substrate and the catalytic-centre activity (‘turnover number‘) for conjugation, perhaps by increasing the proportion of the substrate bound productively. Neither of these two effects of GSH analogues are seen in the C-terminally truncated enzyme, indicating a role for the C-terminal helix in the GSH-induced conformational change.

scholarly journals Discovery and characterization of a sulfoquinovose mutarotase using kinetic analysis at equilibrium by exchange spectroscopy

2018 ◽  
Vol 475 (7) ◽  
pp. 1371-1383 ◽  
Author(s):  
Palika Abayakoon ◽  
James P. Lingford ◽  
Yi Jin ◽  
Christopher Bengt ◽  
Gideon J. Davies ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Active Sites ◽  
Glucuronic Acid ◽  
Chemical Exchange ◽  
Sequence Analyses ◽  
Uncharacterized Gene ◽  
Exchange Spectroscopy ◽  
First Time ◽  
Better Than

Bacterial sulfoglycolytic pathways catabolize sulfoquinovose (SQ), or glycosides thereof, to generate a three-carbon metabolite for primary cellular metabolism and a three-carbon sulfonate that is expelled from the cell. Sulfoglycolytic operons encoding an Embden–Meyerhof–Parnas-like or Entner–Doudoroff (ED)-like pathway harbor an uncharacterized gene (yihR in Escherichia coli; PpSQ1_00415 in Pseudomonas putida) that is up-regulated in the presence of SQ, has been annotated as an aldose-1-epimerase and which may encode an SQ mutarotase. Our sequence analyses and structural modeling confirmed that these proteins possess mutarotase-like active sites with conserved catalytic residues. We overexpressed the homolog from the sulfo-ED operon of Herbaspirillum seropedicaea (HsSQM) and used it to demonstrate SQ mutarotase activity for the first time. This was accomplished using nuclear magnetic resonance exchange spectroscopy, a method that allows the chemical exchange of magnetization between the two SQ anomers at equilibrium. HsSQM also catalyzed the mutarotation of various aldohexoses with an equatorial 2-hydroxy group, including d-galactose, d-glucose, d-glucose-6-phosphate (Glc-6-P), and d-glucuronic acid, but not d-mannose. HsSQM displayed only 5-fold selectivity in terms of efficiency (kcat/KM) for SQ versus the glycolysis intermediate Glc-6-P; however, its proficiency [kuncat/(kcat/KM)] for SQ was 17 000-fold better than for Glc-6-P, revealing that HsSQM preferentially stabilizes the SQ transition state.

Fe-Modified ZSM-5 and β Zeolites for Direct N2O Decomposition

2012 ◽  
Vol 610-613 ◽  
pp. 94-99 ◽  
Author(s):  
Quan Hui Guo ◽  
Juan Li ◽  
Ying Xia Li
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Channel Wall ◽  
Decomposition Reaction ◽  
Catalytic Performance ◽  
Iron Ions ◽  
Exchange Method ◽  
Different Types ◽  
Charge Balancing ◽  
Better Than

Fe-modified ZSM-5 and β zeolites were prepared by adopting liquid ion-exchange method and their catalytic performance was studied in the N2O decomposition reaction. The state of Fe loaded on Fe-zeolites was investigated by means of UV-vis diffuse spectra, infrared spectroscopy, EPR and H2-TPR. The results of IR of hydroxyl stretching and UV-vis investigationSubscript texts indicated that part of the iron-ions was introduced into zeolites at the charge-balancing sites. The results of EPR and H2-TPR investigations showed that the same iron species were loaded on ZSM-5 and β zeolites. However, the results of IR of the perturbed anti-symmetric T-O-T vibrations of iron-ions indicated that different types of ZSM-5 and β zeolites resulted in different distributions of charge-balancing iron cations. The iron-ions could replace Brönsted acid protons at the straight channel wall (α sites), intersection of straight and sinusoidal channels (β sites), and sinusoidal channel wall (γ sites) within the ZSM-5 zeolite. In the case of Fe-β zeolites, iron-ions mainly located in the straight channels. We observed that the catalytic activity of the iron ions located on the α sites of ZSM-5 zeolites was better than those of iron ions located on β and γ sites in N2O direct decomposition, since the former was the most easily reduced from Fe3+to Fe2+in H2. Furthermore, it was found that Fe-β zeolite showed higher catalytic activity than Fe-ZSM-5 zeolite. This difference was attributed to the active sites located almost exclusively in the straight zeolite channels.

scholarly journals Structures of a non-ribosomal peptide synthetase condensation domain suggest the basis of substrate selectivity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Thierry Izoré ◽  
Y. T. Candace Ho ◽  
Joe A. Kaczmarski ◽  
Athina Gavriilidou ◽  
Ka Ho Chow ◽  
...  
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Peptide Bond ◽  
Assembly Lines ◽  
Modular Assembly ◽  
Central Function ◽  
Acceptor Substrate ◽  
Peptide Synthetases ◽  
Peptide Assembly ◽  
Condensation Domain

AbstractNon-ribosomal peptide synthetases are important enzymes for the assembly of complex peptide natural products. Within these multi-modular assembly lines, condensation domains perform the central function of chain assembly, typically by forming a peptide bond between two peptidyl carrier protein (PCP)-bound substrates. In this work, we report structural snapshots of a condensation domain in complex with an aminoacyl-PCP acceptor substrate. These structures allow the identification of a mechanism that controls access of acceptor substrates to the active site in condensation domains. The structures of this complex also allow us to demonstrate that condensation domain active sites do not contain a distinct pocket to select the side chain of the acceptor substrate during peptide assembly but that residues within the active site motif can instead serve to tune the selectivity of these central biosynthetic domains.

scholarly journals Reduction of chlorate and regeneration of activated carbon used for chlorate adsorption

2019 ◽  
Vol 1 (1) ◽  
pp. 72-85 ◽  
Author(s):  
Shyam Lakshmanan ◽  
Yen Li Yung
Keyword(s):  
Activated Carbon ◽  
Active Sites ◽  
Palm Kernel ◽  
Coconut Shell ◽  
Scanning Electron Micrograph ◽  
Palm Kernel Shell ◽  
Chlorine Gas ◽  
Ability To Regenerate ◽  
Enhanced Adsorption ◽  
Better Than

Abstract Activated carbon (AC) from coal, coconut and palm kernel shell was regenerated after adsorbing chlorate from chlor-alkali plant brine solutions. Hydrochloric acid (HCl) of 17% w/w concentration showed the ability to regenerate AC, with some chlorine gas being released. Regeneration with HCl yielded enhanced adsorption of chlorate. AC from coconut shell adsorbed chlorate better than coal and palm kernel shell AC. Higher chlorate concentration in the influent and lower influent pH resulted in better adsorption. Regeneration of the AC with 17% w/w HCl reduced chlorate to chlorine derivatives. The AC released 107 mg/g of chlorine during the first regeneration and 160–178 mg/g after the second regeneration. During regeneration, coal AC released the highest amount of chlorine at 0.51–0.59 mg/g of chlorate adsorbed followed by palm kernel shell with 0.34–0.36 mg/g, while coconut shell AC released 0.18 mg/g. Scanning electron micrograph of the coconut shell AC carried out after each regeneration showed the structure of AC remained intact, with active sites surfacing on the regenerated AC. Using AC for chlorate adsorption followed by regeneration with 17% w/w HCl may reduce the release of brine and chlorate to the environment from chlor-alkali plants.

scholarly journals Enhanced Sulfamerazine Removal via Adsorption–Photocatalysis Using Bi2O3–TiO2/PAC Ternary Nanoparticles

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2273
Author(s):  
Xiaoxuan Zhuang ◽  
Xing Li ◽  
Yanling Yang ◽  
Nan Wang ◽  
Yi Shang ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Mass Transfer ◽  
Active Sites ◽  
Photocatalytic Performance ◽  
Superoxide Radical ◽  
Oxygen Species ◽  
Ring Fracture ◽  
Mass Transfer Mechanism ◽  
Alkaline Conditions ◽  
Better Than

The presence of sulfonamides (SAs) in water has received increasing attention due to the risk to ecosystems. The adsorption and photocatalysis performance for sulfamerazine (SMZ) of Bi2O3–TiO2 supported on powdered activated carbon (Bi2O3–TiO2/PAC) nanoparticles was evaluated. The amount of doped Bi2O3 not only influenced the photocatalytic performance but also impacted the adsorption capacity. The adsorption mass transfer mechanism of Bi2O3–TiO2/PAC was elucidated and is further discussed in combination with the photocatalytic mechanism. It was indicated that Bi2O3–TiO2/PAC(10%–700 °C) performed best, and the SMZ removal by the adsorption–photocatalysis of Bi2O3–TiO2/PAC(10%–700 °C) reached 95.5%. Adsorption onto active sites was a major adsorption step, and external diffusion was assisted. Superoxide radical (●O2−) and hole (h+) were identified as the major reactive oxygen species (ROS) for SMZ removal. Benzene ring fracture, SO2 extrusion and nitrogenated SMZ were proposed as the main pathways for photocatalysis. Meanwhile, alkaline conditions enhanced photocatalytic performance, while contrary effects were observed for adsorption. The adsorption–photocatalysis removal performance for SMZ in lake water was better than that for river water. It can be generalized for the potential application of photocatalysis coupling with adsorption to remove refractory antibiotics in water.

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