First-Sphere and Second-Sphere Electrostatic Effects in the Active Site of a Class Mu Glutathione Transferase†,‡

Biochemistry ◽  
1996 ◽  
Vol 35 (15) ◽  
pp. 4753-4765 ◽  
Author(s):  
Gaoyi Xiao ◽  
Suxing Liu ◽  
Xinhua Ji ◽  
William W. Johnson ◽  
Jihong Chen ◽  
...  
Keyword(s):  
Active Site ◽  
Glutathione Transferase ◽  
Electrostatic Effects

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 Multiphasic denaturation of glutathione transferase B1-1 by guanidinium chloride. Role of the dimeric structure on the flexibility of the active site

1993 ◽  
Vol 215 (3) ◽  
pp. 741-745 ◽  
Author(s):  
Paolo SACCHETTA ◽  
Antonio ACETO ◽  
Tonino BUCCIARELLI ◽  
Beatrice DRAGANI ◽  
Stella SANTARONE ◽  
...  
Keyword(s):  
Active Site ◽  
Glutathione Transferase ◽  
Guanidinium Chloride ◽  
Dimeric Structure

scholarly journals Chemical modification of rat liver microsomal glutathione transferase defines residues of importance for catalytic function

1990 ◽  
Vol 272 (2) ◽  
pp. 479-484 ◽  
Author(s):  
C Andersson ◽  
R Morgenstern
Keyword(s):  
Chemical Modification ◽  
Rat Liver ◽  
Active Site ◽  
Glutathione Transferase ◽  
Amino Acid Residues ◽  
Active Site Residues ◽  
Histidine Residues ◽  
Catalytic Function ◽  
Low Efficiency ◽  
Microsomal Glutathione

Amino acid residues that are essential for the activity of rat liver microsomal glutathione transferase have been identified using chemical modification with various group-selective reagents. The enzyme reconstituted into phosphatidylcholine liposomes does not require stabilization with glutathione for activity (in contrast with the purified enzyme in detergent) and can thus be used for modification of active-site residues. Protection by the product analogue and inhibitor S-hexylglutathione was used as a criterion for specificity. It was shown that the histidine-selective reagent diethylpyrocarbonate inactivated the enzyme and that S-hexylglutathione partially protected against this inactivation. All three histidine residues in microsomal glutathione transferase could be modified, albeit at different rates. Inactivation of 90% of enzyme activity was achieved within the time period required for modification of the most reactive histidine, indicating the functional importance of this residue in catalysis. The arginine-selective reagents phenylglyoxal and 2,3-butanedione inhibited the enzyme, but the latter with very low efficiency; therefore no definitive assignment of arginine as essential for the activity of microsomal glutathione transferase can be made. The amino-group-selective reagents 2,4,6-trinitrobenzenesulphonate and pyridoxal 5′-phosphate inactivated the enzyme. Thus histidine residues and amino groups are suggested to be present in the active site of the microsomal glutathione transferase.

Valine 10 May Act as a Driver for Product Release from the Active Site of Human Glutathione Transferase P1-1†,‡

Biochemistry ◽  
2000 ◽  
Vol 39 (51) ◽  
pp. 15961-15970 ◽  
Author(s):  
Chiara Micaloni ◽  
Anna P. Mazzetti ◽  
Marzia Nuccetelli ◽  
Jamie Rossjohn ◽  
William J. McKinstry ◽  
...  
Keyword(s):  
Active Site ◽  
Glutathione Transferase ◽  
Product Release

scholarly journals Identification, characterization and structure of a new Delta class glutathione transferase isoenzyme

2005 ◽  
Vol 388 (3) ◽  
pp. 763-771 ◽  
Author(s):  
Rungrutai UDOMSINPRASERT ◽  
Saengtong PONGJAROENKIT ◽  
Jantana WONGSANTICHON ◽  
Aaron J. OAKLEY ◽  
La-aied PRAPANTHADARA ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Fatty Acids ◽  
Active Site ◽  
Glutathione Transferase ◽  
Putative Promoter ◽  
Anopheles Dirus ◽  
Adult Females ◽  
Genes Encoding ◽  
Supergene Family ◽  
Gst Activity

The insect GST (glutathione transferase) supergene family encodes a varied group of proteins belonging to at least six individual classes. Interest in insect GSTs has focused on their role in conferring insecticide resistance. Previously from the mosquito malaria vector Anopheles dirus, two genes encoding five Delta class GSTs have been characterized for structural as well as enzyme activities. We have obtained a new Delta class GST gene and isoenzyme from A. dirus, which we name adGSTD5-5. The adGSTD5-5 isoenzyme was identified and was only detectably expressed in A. dirus adult females. A putative promoter analysis suggests that this GST has an involvement in oogenesis. The enzyme displayed little activity for classical GST substrates, although it possessed the greatest activity for DDT [1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane] observed for Delta GSTs. However, GST activity was inhibited or enhanced in the presence of various fatty acids, suggesting that the enzyme may be modulated by fatty acids. We obtained a crystal structure for adGSTD5-5 and compared it with other Delta GSTs, which showed that adGSTD5-5 possesses an elongated and more polar active-site topology.

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