Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4
High concentrations of electrophilic lipid alkenals formed during oxidative stress are implicated in cytotoxicity and disease. However, low concentrations of alkenals are required to induce antioxidative stress responses. An established clearance pathway for lipid alkenals includes conjugation to gl...
| 主要な著者: | , , , , |
|---|---|
| フォーマット: | 論文 |
| 言語: | English |
| 出版事項: |
MDPI AG
2023-02-01
|
| シリーズ: | Biomolecules |
| 主題: | |
| オンライン･アクセス: | https://www.mdpi.com/2218-273X/13/2/329 |
| _version_ | 1827758373858181120 |
|---|---|
| author | Michele Scian Lorela Paço Taylor A. Murphree Laura M. Shireman William M. Atkins |
| author_facet | Michele Scian Lorela Paço Taylor A. Murphree Laura M. Shireman William M. Atkins |
| author_sort | Michele Scian |
| collection | DOAJ |
| description | High concentrations of electrophilic lipid alkenals formed during oxidative stress are implicated in cytotoxicity and disease. However, low concentrations of alkenals are required to induce antioxidative stress responses. An established clearance pathway for lipid alkenals includes conjugation to glutathione (GSH) via Michael addition, which is catalyzed mainly by glutathione transferase isoform A4 (GSTA4-4). Based on the ability of GSTs to catalyze hydrolysis or <i>retro</i>-Michael addition of GSH conjugates, and the antioxidant function of low concentrations of lipid alkenals, we hypothesize that GSTA4-4 contributes a homeostatic role in lipid metabolism. Enzymatic kinetic parameters for <i>retro</i>-Michael addition with trans-2-Nonenal (NE) reveal the chemical competence of GSTA4-4 in this putative role. The forward GSTA4-4-catalyzed Michael addition occurs with the rapid exchange of the C2 proton of NE in D<sub>2</sub>O as observed by NMR. The isotope exchange was completely dependent on the presence of GSH. The overall commitment to catalysis, or the ratio of first order k<sub>cat,f</sub> for ‘forward’ Michael addition to the first order k<sub>cat,ex</sub> for H/D exchange is remarkably low, approximately 3:1. This behavior is consistent with the possibility that GSTA4-4 is a regulatory enzyme that contributes to steady-state levels of lipid alkenals, rather than a strict ‘one way’ detoxication enzyme. |
| first_indexed | 2024-03-11T09:06:25Z |
| format | Article |
| id | doaj.art-e270b1016b824c80bcc9e3e37b0b99f2 |
| institution | Directory Open Access Journal |
| issn | 2218-273X |
| language | English |
| last_indexed | 2024-03-11T09:06:25Z |
| publishDate | 2023-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Biomolecules |
| spelling | doaj.art-e270b1016b824c80bcc9e3e37b0b99f22023-11-16T19:23:39ZengMDPI AGBiomolecules2218-273X2023-02-0113232910.3390/biom13020329Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4Michele Scian0Lorela Paço1Taylor A. Murphree2Laura M. Shireman3William M. Atkins4Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195-7610, USADepartment of Medicinal Chemistry, University of Washington, Seattle, WA 98195-7610, USADepartment of Medicinal Chemistry, University of Washington, Seattle, WA 98195-7610, USADepartment of Medicinal Chemistry, University of Washington, Seattle, WA 98195-7610, USADepartment of Medicinal Chemistry, University of Washington, Seattle, WA 98195-7610, USAHigh concentrations of electrophilic lipid alkenals formed during oxidative stress are implicated in cytotoxicity and disease. However, low concentrations of alkenals are required to induce antioxidative stress responses. An established clearance pathway for lipid alkenals includes conjugation to glutathione (GSH) via Michael addition, which is catalyzed mainly by glutathione transferase isoform A4 (GSTA4-4). Based on the ability of GSTs to catalyze hydrolysis or <i>retro</i>-Michael addition of GSH conjugates, and the antioxidant function of low concentrations of lipid alkenals, we hypothesize that GSTA4-4 contributes a homeostatic role in lipid metabolism. Enzymatic kinetic parameters for <i>retro</i>-Michael addition with trans-2-Nonenal (NE) reveal the chemical competence of GSTA4-4 in this putative role. The forward GSTA4-4-catalyzed Michael addition occurs with the rapid exchange of the C2 proton of NE in D<sub>2</sub>O as observed by NMR. The isotope exchange was completely dependent on the presence of GSH. The overall commitment to catalysis, or the ratio of first order k<sub>cat,f</sub> for ‘forward’ Michael addition to the first order k<sub>cat,ex</sub> for H/D exchange is remarkably low, approximately 3:1. This behavior is consistent with the possibility that GSTA4-4 is a regulatory enzyme that contributes to steady-state levels of lipid alkenals, rather than a strict ‘one way’ detoxication enzyme.https://www.mdpi.com/2218-273X/13/2/329enzyme detoxicationsubstrate promiscuityhydroxynonenallipid peroxidationlipid alkenalsenzyme mechanism |
| spellingShingle | Michele Scian Lorela Paço Taylor A. Murphree Laura M. Shireman William M. Atkins Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4 Biomolecules enzyme detoxication substrate promiscuity hydroxynonenal lipid peroxidation lipid alkenals enzyme mechanism |
| title | Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4 |
| title_full | Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4 |
| title_fullStr | Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4 |
| title_full_unstemmed | Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4 |
| title_short | Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4 |
| title_sort | reversibility and low commitment to forward catalysis in the conjugation of lipid alkenals by glutathione transferase a4 4 |
| topic | enzyme detoxication substrate promiscuity hydroxynonenal lipid peroxidation lipid alkenals enzyme mechanism |
| url | https://www.mdpi.com/2218-273X/13/2/329 |
| work_keys_str_mv | AT michelescian reversibilityandlowcommitmenttoforwardcatalysisintheconjugationoflipidalkenalsbyglutathionetransferasea44 AT lorelapaco reversibilityandlowcommitmenttoforwardcatalysisintheconjugationoflipidalkenalsbyglutathionetransferasea44 AT tayloramurphree reversibilityandlowcommitmenttoforwardcatalysisintheconjugationoflipidalkenalsbyglutathionetransferasea44 AT lauramshireman reversibilityandlowcommitmenttoforwardcatalysisintheconjugationoflipidalkenalsbyglutathionetransferasea44 AT williammatkins reversibilityandlowcommitmenttoforwardcatalysisintheconjugationoflipidalkenalsbyglutathionetransferasea44 |