scholarly journals Epsilon glutathione transferases possess a unique class-conserved subunit interface motif that directly interacts with glutathione in the active site

2015 ◽  
Vol 35 (6) ◽  
Author(s):  
Jantana Wongsantichon ◽  
Robert C. Robinson ◽  
Albert J. Ketterman
Keyword(s):  
Drosophila Melanogaster ◽  
Active Site ◽  
Active Sites ◽  
Glutathione Transferase ◽  
Glutathione Transferases ◽  
Conserved Motif ◽  
Subunit Interface ◽  
Dimeric Subunit

Analysis of a new structure of an Epsilon class glutathione transferase from Drosophila melanogaster reveals a highly conserved motif that spans the dimeric subunit interface and connects the two active sites.

scholarly journals The Role of Glutathione in the Isomerization of Δ5-Androstene- 3,17-dione Catalyzed by Human Glutathione Transferase A1-1

2001 ◽  
Vol 276 (15) ◽  
pp. 11698-11704 ◽  
Author(s):  
Pär L. Pettersson ◽  
Bengt Mannervik
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Catalytic Mechanism ◽  
Glutathione Transferase ◽  
Ph Dependence ◽  
Enzymatic Catalysis ◽  
Catalytic Efficiency ◽  
Protonated Form ◽  
Hydroxyl Group ◽  
Isomerization Reaction

Human glutathione transferase (GST) A1-1 efficiently catalyzes the isomerization of Δ5-androstene-3,17-dione (AD) into Δ4-androstene-3,17-dione. High activity requires glutathione, but enzymatic catalysis occurs also in the absence of this cofactor. Glutathione alone shows a limited catalytic effect.S-Alkylglutathione derivatives do not promote the reaction, and the pH dependence of the isomerization indicates that the glutathione thiolate serves as a base in the catalytic mechanism. Mutation of the active-site Tyr9into Phe significantly decreases the steady-state kinetic parameters, alters their pH dependence, and increases the pKavalue of the enzyme-bound glutathione thiol. Thus, Tyr9promotes the reaction via its phenolic hydroxyl group in protonated form. GST A2-2 has a catalytic efficiency with AD 100-fold lower than the homologous GST A1-1. Another Alpha class enzyme, GST A4-4, is 1000-fold less active than GST A1-1. The Y9F mutant of GST A1-1 is more efficient than GST A2-2 and GST A4-4, both having a glutathione cofactor and an active-site Tyr9residue. The active sites of GST A2-2 and GST A1-1 differ by only four amino acid residues, suggesting that proper orientation of AD in relation to the thiolate of glutathione is crucial for high catalytic efficiency in the isomerization reaction. The GST A1-1-catalyzed steroid isomerization provides a complement to the previously described isomerase activity of 3β-hydroxysteroid dehydrogenase.

scholarly journals Differences in the subunit interface residues of alternatively spliced glutathione transferases affects catalytic and structural functions

2007 ◽  
Vol 401 (3) ◽  
pp. 635-644 ◽  
Author(s):  
Juthamart Piromjitpong ◽  
Jantana Wongsantichon ◽  
Albert J. Ketterman
Keyword(s):  
Active Site ◽  
Electrostatic Interactions ◽  
Hydrophobic Interactions ◽  
Glutathione Transferases ◽  
Active Site Residues ◽  
Interface Area ◽  
Subunit Interface ◽  
Alternatively Spliced ◽  
Active Site Conformation ◽  
Interface Residues

GSTs (glutathione transferases) are multifunctional widespread enzymes. Currently there are 13 identified classes within this family. Previously most structural characterization has been reported for mammalian Alpha, Mu and Pi class GSTs. In the present study we characterize two enzymes from the insect-specific Delta class, adGSTD3-3 and adGSTD4-4. These two proteins are alternatively spliced products from the same gene and have very similar tertiary structures. Several major contributions to the dimer interface area can be separated into three regions: conserved electrostatic interactions in region 1, hydrophobic interactions in region 2 and an ionic network in region 3. The four amino acid side chains studied in region 1 interact with each other as a planar rectangle. These interactions are highly conserved among the GST classes, Delta, Sigma and Theta. The hydrophobic residues in region 2 are not only subunit interface residues but also active site residues. Overall these three regions provide important contributions to stabilization and folding of the protein. In addition, decreases in yield as well as catalytic activity changes, suggest that the mutations in these regions can disrupt the active site conformation which decreases binding affinity, alters kinetic constants and alters substrate specificity. Several of these residues have only a slight effect on the initial folding of each subunit but have more influence on the dimerization process as well as impacting upon appropriate active site conformation. The results also suggest that even splicing products from the same gene may have specific features in the subunit interface area that would preclude heterodimerization.

scholarly journals Proposed Mechanism for Monomethylarsonate Reductase Activity of Human Omega-class Glutathione Transferase GSTO1

2021 ◽  
Author(s):  
Aaron J Oakley
Keyword(s):  
Binding Site ◽  
Active Site ◽  
Binding Sites ◽  
Glutathione Transferase ◽  
Reductase Activity ◽  
Inorganic Arsenic ◽  
Glutathione Transferases ◽  
Public Health Issue ◽  
Major Public Health Issue ◽  
Glutathione Binding

Contamination of drinking water with toxic inorganic arsenic is a major public health issue. The mechanisms of enzymes and transporters in arsenic elimination are therefore of interest. The human omega-class glutathione transferases have been previously shown to possess monomethylarsonate (V) reductase activity. To further understanding of this activity, molecular dynamics of human GSTO1-1 bound to glutathione with a monomethylarsonate isostere were simulated to reveal putative monomethylarsonate binding sites on the enzyme. The major binding site is in the active site, adjacent to the glutathione binding site. Based on this and previously reported biochemical data, a reaction mechanism for this enzyme is proposed. Further insights were gained from comparison of the human omega-class GSTs to homologs from a range of animals.

scholarly journals Photoaffinity labelling of the active site of the rat glutathione transferases 3-3 and 1-1 and human glutathione transferase A1-1

1994 ◽  
Vol 302 (2) ◽  
pp. 383-390 ◽  
Author(s):  
R J Cooke ◽  
R Björnestedt ◽  
K T Douglas ◽  
J H McKie ◽  
M D King ◽  
...  
Keyword(s):  
Rat Liver ◽  
Active Site ◽  
Glutathione Transferase ◽  
Competitive Inhibitor ◽  
Glutathione Transferases ◽  
Molecular Graphics ◽  
Hydrophobic Region ◽  
Preparative Scale ◽  
Photoaffinity Labelling ◽  
Wide Range

The glutathione transferases (GSTs) form a group of enzymes responsible for a wide range of molecular detoxications. The photoaffinity label S-(2-nitro-4-azidophenyl)glutathione was used to study the hydrophobic region of the active site of the rat liver GST 1-1 and 2-2 isoenzymes (class Alpha) as well as the rat class-Mu GST 3-3. Photoaffinity labelling was carried out using a version of S-(2-nitro-4-azidophenyl)glutathione tritiated in the arylazido ring. The labelling occurred with higher levels of radioisotope incorporation for the Mu than the Alpha families. Taking rat GST 3-3, 1.18 (+/- 0.05) mol of radiolabel from S-(2-nitro-4-azidophenyl)glutathione was incorporated per mol of dimeric enzyme, which could be blocked by the presence of the strong competitive inhibitor, S-tritylglutathione (Ki = 1.4 x 10(-7) M). Radiolabelling of the protein paralleled the loss of enzyme activity. Photoaffinity labelling by tritiated S-(2-nitro-4-azidophenyl)glutathione on a preparative scale (in the presence and absence of S-tritylglutathione) followed by tryptic digestion and purification of the labelled peptides indicated that GST 3-3 was specifically photolabelled; the labelled peptides were sequenced. Similarly, preparative photoaffinity labelling by S-(2-nitro-4-azidophenyl)glutathione of the rat liver 1-1 isoenzyme, the human GST A1-1 and the human-rat chimaeric GST, H1R1/1, was carried out with subsequent sequencing of radiolabelled h.p.l.c.-purified tryptic peptides. The results were interpreted by means of molecular-graphics analysis to locate photoaffinity-labelled peptides using the X-ray-crystallographic co-ordinates of rat GST 3-3 and human GST A1-1. The molecular-graphical analysis indicated that the labelled peptides are located within the immediate vicinity of the region occupied by S-substituted glutathione derivatives bound in the active-site cavity of the GSTs investigated.

scholarly journals Human Glutathione Transferase T2-2 Discloses Some Evolutionary Strategies for Optimization of Substrate Binding to the Active Site of Glutathione Transferases

2000 ◽  
Vol 276 (8) ◽  
pp. 5427-5431 ◽  
Author(s):  
Anna Maria Caccuri ◽  
Giovanni Antonini ◽  
Philip G. Board ◽  
Jack Flanagan ◽  
Michael W. Parker ◽  
...  
Keyword(s):  
Active Site ◽  
Glutathione Transferase ◽  
Substrate Binding ◽  
Glutathione Transferases ◽  
Evolutionary Strategies

scholarly journals Structure-activity relationships of 4-hydroxyalkenals in the conjugation catalysed by mammalian glutathione transferases

1987 ◽  
Vol 247 (3) ◽  
pp. 707-713 ◽  
Author(s):  
U H Danielson ◽  
H Esterbauer ◽  
B Mannervik
Keyword(s):  
Chain Length ◽  
Active Site ◽  
Glutathione Transferase ◽  
Physiological Role ◽  
Catalytic Efficiency ◽  
Glutathione Transferases ◽  
Side Chain ◽  
Structure Activity ◽  
Cytosolic Glutathione ◽  
Free Energy Of Binding

The substrate specificities of 15 cytosolic glutathione transferases from rat, mouse and man have been explored by use of a homologous series of 4-hydroxyalkenals, extending from 4-hydroxypentenal to 4-hydroxypentadecenal. Rat glutathione transferase 8-8 is exceptionally active with the whole range of 4-hydroxyalkenals, from C5 to C15. Rat transferase 1-1, although more than 10-fold less efficient than transferase 8-8, is the second most active transferase with the longest chain length substrates. Other enzyme forms showing high activities with these substrates are rat transferase 4-4 and human transferase mu. The specificity constants, kcat./Km, for the various enzymes have been determined with the 4-hydroxyalkenals. From these constants the incremental Gibbs free energy of binding to the enzyme has been calculated for the homologous substrates. The enzymes responded differently to changes in the length of the hydrocarbon side chain and could be divided into three groups. All glutathione transferases displayed increased binding energy in response to increased hydrophobicity of the substrate. For some of the enzymes, steric limitations of the active site appear to counteract the increase in binding strength afforded by increased chain length of the substrate. Comparison of the activities with 4-hydroxyalkenals and other activated alkenes provides information about the active-site properties of certain glutathione transferases. The results show that the ensemble of glutathione transferases in a given species may serve an important physiological role in the conjugation of the whole range of 4-hydroxyalkenals. In view of its high catalytic efficiency with all the homologues, rat glutathione transferase 8-8 appears to have evolved specifically to serve in the detoxication of these reactive compounds of oxidative metabolism.

Catalytic Resonance Theory: Parallel Reaction Pathway Control

2019 ◽  
Author(s):  
M. Alexander Ardagh ◽  
Manish Shetty ◽  
Anatoliy Kuznetsov ◽  
Qi Zhang ◽  
Phillip Christopher ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
Active Site ◽  
Active Sites ◽  
Reaction Pathway ◽  
Control Strategies ◽  
Oscillation Amplitude ◽  
Catalytic Performance ◽  
Parallel Reaction ◽  
Resonance Theory ◽  
Static Conditions

Catalytic enhancement of chemical reactions via heterogeneous materials occurs through stabilization of transition states at designed active sites, but dramatically greater rate acceleration on that same active site is achieved when the surface intermediates oscillate in binding energy. The applied oscillation amplitude and frequency can accelerate reactions orders of magnitude above the catalytic rates of static systems, provided the active site dynamics are tuned to the natural frequencies of the surface chemistry. In this work, differences in the characteristics of parallel reactions are exploited via selective application of active site dynamics (0 < ΔU < 1.0 eV amplitude, 10<sup>-6</sup> < f < 10<sup>4</sup> Hz frequency) to control the extent of competing reactions occurring on the shared catalytic surface. Simulation of multiple parallel reaction systems with broad range of variation in chemical parameters revealed that parallel chemistries are highly tunable in selectivity between either pure product, even when specific products are not selectively produced under static conditions. Two mechanisms leading to dynamic selectivity control were identified: (i) surface thermodynamic control of one product species under strong binding conditions, or (ii) catalytic resonance of the kinetics of one reaction over the other. These dynamic parallel pathway control strategies applied to a host of chemical conditions indicate significant potential for improving the catalytic performance of many important industrial chemical reactions beyond their existing static performance.

Porcine glutathione transferase Alpha 2-2 is a human GST A3-3 analogue that catalyses steroid double-bond isomerization

2010 ◽  
Vol 431 (1) ◽  
pp. 159-167 ◽  
Author(s):  
Natalia Fedulova ◽  
Françoise Raffalli-Mathieu ◽  
Bengt Mannervik
Keyword(s):  
Double Bond ◽  
Glutathione Transferase ◽  
Biological Species ◽  
Glutathione Transferases ◽  
Special Role ◽  
Primary Role ◽  
The Novel ◽  
Protective Function ◽  
Isomerase Activity

A primary role of GSTs (glutathione transferases) is detoxication of electrophilic compounds. In addition to this protective function, hGST (human GST) A3-3, a member of the Alpha class of soluble GSTs, has prominent steroid double-bond isomerase activity. The isomerase reaction is an obligatory step in the biosynthesis of steroid hormones, indicating a special role of hGST A3-3 in steroidogenic tissues. An analogous GST with high steroid isomerase activity has so far not been found in any other biological species. In the present study, we characterized a Sus scrofa (pig) enzyme, pGST A2-2, displaying high steroid isomerase activity. High levels of pGST A2-2 expression were found in ovary, testis and liver. In its functional properties, other than steroid isomerization, pGST A2-2 was most similar to hGST A3-3. The properties of the novel porcine enzyme lend support to the notion that particular GSTs play an important role in steroidogenesis.

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