scholarly journals Clarification of the role of key active site residues of glutathione transferase Zeta/maleylacetoacetate isomerase by a new spectrophotometric technique

2003 ◽  
Vol 374 (3) ◽  
pp. 731-737 ◽  
Author(s):  
Philip G. BOARD ◽  
Matthew C. TAYLOR ◽  
Marjorie COGGAN ◽  
Michael W. PARKER ◽  
Hoffman B. LANTUM ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Active Site ◽  
Glutathione Transferase ◽  
Salt Bridge ◽  
Side Chain ◽  
Active Site Residues ◽  
Conserved Residues ◽  
Isomerase Activity ◽  
Catalytic Role

hGSTZ1-1 (human glutathione transferase Zeta 1-1) catalyses a range of glutathione-dependent reactions and plays an important role in the metabolism of tyrosine via its maleylacetoacetate isomerase activity. The crystal structure and sequence alignment of hGSTZ1 with other GSTs (glutathione transferases) focused attention on three highly conserved residues (Ser-14, Ser-15, Cys-16) as candidates for an important role in catalysis. Progress in the investigation of these residues has been limited by the absence of a convenient assay for kinetic analysis. In this study we have developed a new spectrophotometric assay with a novel substrate [(±)-2-bromo-3-(4-nitrophenyl)propionic acid]. The assay has been used to rapidly assess the potential catalytic role of several residues in the active site. Despite its less favourable orientation in the crystal structure, Ser-14 was the only residue found to be essential for catalysis. It is proposed that a conformational change may favourably reposition the hydroxyl of Ser-14 during the catalytic cycle. The Cys16→Ala (Cys-16 mutated to Ala) mutation caused a dramatic increase in the Km for glutathione, indicating that Cys-16 plays an important role in the binding and orientation of glutathione in the active site. Previous structural studies implicated Arg-175 in the orientation of α-halo acid substrates in the active site of hGSTZ1-1. Mutation of Arg-175 to Lys or Ala resulted in a significant lowering of the kcat in the Ala-175 variant. This result is consistent with the proposal that the charged side chain of Arg-175 forms a salt bridge with the carboxylate of the α-halo acid substrates.

scholarly journals Analyzing the catalytic role of active site residues in the Fe-type nitrile hydratase from Comamonas testosteroni Ni1

2015 ◽  
Vol 20 (5) ◽  
pp. 885-894 ◽  
Author(s):  
Salette Martinez ◽  
Rui Wu ◽  
Karoline Krzywda ◽  
Veronika Opalka ◽  
Hei Chan ◽  
...  
Keyword(s):  
Active Site ◽  
Nitrile Hydratase ◽  
Comamonas Testosteroni ◽  
Active Site Residues ◽  
Catalytic Role

scholarly journals Characterization of Glycerol Trinitrate Reductase (NerA) and the Catalytic Role of Active-Site Residues

2004 ◽  
Vol 186 (6) ◽  
pp. 1802-1810 ◽  
Author(s):  
Samantha J. Marshall ◽  
Doreen Krause ◽  
Dayle K. Blencowe ◽  
Graham F. White
Keyword(s):  
Active Site ◽  
Structural Model ◽  
Flavin Mononucleotide ◽  
Active Site Residues ◽  
Old Yellow Enzyme ◽  
Ping Pong ◽  
Glycerol Trinitrate ◽  
Catalytic Role

ABSTRACT Glycerol trinitrate reductase (NerA) from Agrobacterium radiobacter, a member of the old yellow enzyme (OYE) family of oxidoreductases, was expressed in and purified from Escherichia coli. Denaturation of pure enzyme liberated flavin mononucleotide (FMN), and spectra of NerA during reduction and reoxidation confirmed its catalytic involvement. Binding of FMN to apoenzyme to form the holoenzyme occurred with a dissociation constant of ca. 10−7 M and with restoration of activity. The NerA-dependent reduction of glycerol trinitrate (GTN; nitroglycerin) by NADH followed ping-pong kinetics. A structural model of NerA based on the known coordinates of OYE showed that His-178, Asn-181, and Tyr-183 were close to FMN in the active site. The NerA mutation H178A produced mutant protein with bound FMN but no activity toward GTN. The N181A mutation produced protein that did not bind FMN and was isolated in partly degraded form. The mutation Y183F produced active protein with the same k cat as that of wild-type enzyme but with altered Km values for GTN and NADH, indicating a role for this residue in substrate binding. Correlation of the ratio of Km GTN to Km NAD(P)H, with sequence differences for NerA and several other members of the OYE family of oxidoreductases that reduce GTN, indicated that Asn-181 and a second Asn-238 that lies close to Tyr-183 in the NerA model structure may influence substrate specificity.

scholarly journals Evaluation of the role of two conserved active-site residues in Beta class glutathione S-transferases

2000 ◽  
Vol 351 (2) ◽  
pp. 341-346 ◽  
Author(s):  
Nerino ALLOCATI ◽  
Enrico CASALONE ◽  
Michele MASULLI ◽  
Galina POLEKHINA ◽  
Jamie ROSSJOHN ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thermal Stability ◽  
Catalytic Activity ◽  
Proteus Mirabilis ◽  
Active Site ◽  
Binding Capacity ◽  
Active Site Residues ◽  
Terminal Domain ◽  
Glutathione S Transferases

Glutathione S-transferases (GSTs) normally use hydroxy-group-containing residues in the N-terminal domain of the enzyme for stabilizing the activated form of the co-substrate, glutathione. However, previous mutagenesis studies have shown that this is not true for Beta class GSTs and thus the origin of the stabilization remains a mystery. The recently determined crystal structure of Proteus mirabilis GST B1-1 (PmGST B1-1) suggested that the stabilizing role might be fulfilled in Beta class GSTs by one or more residues in the C-terminal domain of the enzyme. To test this hypothesis we mutated His106 and Lys107 of PmGST B1-1 to investigate their possible role in the enzyme's catalytic activity. His106 was mutated to Ala, Asn and Phe, and Lys107 to Ala and Arg. The effects of the replacement on the activity, thermal stability and antibiotic-binding capacity of the enzyme were examined. The results are consistent with the involvement of His106 and Lys107 in interacting with glutathione at the active site but these residues do not contribute significantly to catalysis, folding or antibiotic binding.

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.

Crystal structure of acetylxylan esterase from Caldanaerobacter subterraneus subsp. tengcongensis

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Kohei Sasamoto ◽  
Tomoki Himiyama ◽  
Kunihiko Moriyoshi ◽  
Takashi Ohmoto ◽  
Koichi Uegaki ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Cellulose Acetate ◽  
Electron Density ◽  
Active Site ◽  
Catalytic Domain ◽  
Crystal Packing ◽  
Signal Sequence ◽  
Industrial Applications ◽  
Side Chain ◽  
Active Site Conformation

The acetylxylan esterases (AXEs) classified into carbohydrate esterase family 4 (CE4) are metalloenzymes that catalyze the deacetylation of acetylated carbohydrates. AXE from Caldanaerobacter subterraneus subsp. tengcongensis (TTE0866), which belongs to CE4, is composed of three parts: a signal sequence (residues 1–22), an N-terminal region (NTR; residues 23–135) and a catalytic domain (residues 136–324). TTE0866 catalyzes the deacetylation of highly substituted cellulose acetate and is expected to be useful for industrial applications in the reuse of resources. In this study, the crystal structure of TTE0866 (residues 23–324) was successfully determined. The crystal diffracted to 1.9 Å resolution and belonged to space group I212121. The catalytic domain (residues 136–321) exhibited a (β/α)7-barrel topology. However, electron density was not observed for the NTR (residues 23–135). The crystal packing revealed the presence of an intermolecular space without observable electron density, indicating that the NTR occupies this space without a defined conformation or was truncated during the crystallization process. Although the active-site conformation of TTE0866 was found to be highly similar to those of other CE4 enzymes, the orientation of its Trp264 side chain near the active site was clearly distinct. The unique orientation of the Trp264 side chain formed a different-shaped cavity within TTE0866, which may contribute to its reactivity towards highly substituted cellulose acetate.

Synthesis, characterization and molecular docking studies on some new N-substituted 2-phenylpyrido[2,3-d]pyrimidine derivatives

2021 ◽  
pp. 3846-3854
Author(s):  
Vivek B. Panchabhai ◽  
Santosh R. Butle ◽  
Parag G. Ingole
Keyword(s):  
Crystal Structure ◽  
Antibacterial Activity ◽  
Molecular Docking ◽  
Active Site ◽  
Docking Studies ◽  
Biotin Carboxylase ◽  
Active Site Residues ◽  
Pyrimidine Derivatives ◽  
Molecular Docking Studies ◽  
Novel Scaffold

We report a novel scaffold of N-substituted 2-phenylpyrido(2,3-d)pyrimidine derivatives with potent antibacterial activity by targeting this biotin carboxylase enzyme. The series of eighteen N-substituted 2-phenylpyrido(2,3-d)pyrimidine derivatives were synthesized, characterized and further molecular docking studied to determine the mode of binding and energy changes with the crystal structure of biotin carboxylase (PDB ID: 2V58) was employed as the receptor with compounds 6a-r as ligands. The results obtained from the simulation were obtained in the form of dock score; these values represent the minimum energies. Compounds 6d, 6l, 6n, 6o, 6r and 6i showed formation of hydrogen bonds with the active site residues and van Der Walls interactions with the biotin carboxylase enzyme in their molecular docking studies. This compound can be studied further and developed into a potential antibacterial lead molecule.

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