| 1. |
- Balogh, Larissa M., et al.
(författare)
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Substrate Specificity Combined with Stereopromiscuity in Glutathione Transferase A4-4-Dependent Metabolism of 4-Hydroxynonenal
- 2010
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 49:7, s. 1541-1548
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Tidskriftsartikel (refereegranskat)abstract
- Conjugation to glutathione (GSH) by glutathione transferase A4-4 (GSTA4-4) is a major route of elimination for the lipid peroxidation product 4-hydroxynonenal (HNE), a toxic compound that contributes to numerous diseases. Both enantiomers of HNE are presumed to be toxic, and GSTA4-4 has negligible stereoselectivity toward them, despite its high catalytic chemospecificity for alkenals. In contrast to the highly flexible, and substrate promiscuous, GSTA1-1 isoform that has poor catalytic efficiency with HNE, GSTA4-4 has been postulated to be a rigid template that is preorganized for HNE metabolism. However, the combination of high substrate chemoselectivity and low substrate stereoselectivity is intriguing. The mechanism by which GSTA4-4 achieves this combination is important, because it must metabolize both enantiomers of HNE to efficiently detoxify the biologically formed mixture. The crystal structures of GSTA4-4 and ail engineered variant of GSTA1-1 with high catalytic efficiency toward HNE, cocrystallized with a GSH-HNE conjugate analogue, demonstrate that GSTA4-4 undergoes no enantiospecific induced fit; instead, the active site residue Arg15 is ideally located to interact with the 4-hydroxyl group of either HNE enantiomer. The results reveal an evolutionary strategy for achieving biologically useful stereopromiscuity toward a toxic racemate, concomitant with high catalytic efficiency and substrate specificity toward ail endogenously formed toxin.
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| 2. |
- Scian, Michele, et al.
(författare)
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Comparison of epsilon- and delta-class glutathione S-transferases : the crystal structures of the glutathione S-transferases DmGSTE6 and DmGSTE7 from Drosophila melanogaster
- 2015
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Ingår i: Acta Crystallographica Section D. - 0907-4449 .- 1399-0047. ; 71, s. 2089-2098
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Tidskriftsartikel (refereegranskat)abstract
- Cytosolic glutathione transferases (GSTs) comprise a large family of enzymes with canonical structures that diverge functionally and structurally among mammals, invertebrates and plants. Whereas mammalian GSTs have been characterized extensively with regard to their structure and function, invertebrate GSTs remain relatively unstudied. The invertebrate GSTs do, however, represent potentially important drug targets for infectious diseases and agricultural applications. In addition, it is essential to fully understand the structure and function of invertebrate GSTs, which play important roles in basic biological processes. Invertebrates harbor delta-and epsilon-class GSTs, which are not found in other organisms. Drosophila melanogaster GSTs (DmGSTs) are likely to contribute to detoxication or antioxidative stress during development, but they have not been fully characterized. Here, the structures of two epsilon-class GSTs from Drosophila, DmGSTE6 and DmGSTE7, are reported at 2.1 and 1.5 angstrom resolution, respectively, and are compared with other GSTs to identify structural features that might correlate with their biological functions. The structures of DmGSTE6 and DmGSTE7 are remarkably similar; the structures do not reveal obvious sources of the minor functional differences that have been observed. The main structural difference between the epsilon-and delta-class GSTs is the longer helix (A8) at the C-termini of the epsilon-class enzymes.
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