Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
The glutathione S-transferases : kinetics, binding and inhibition
The glutathione S-transferases are a group of enzymes which catalyse the conjugation of reduced glutathione with a variety of electrophilic molecules, and they are therefore thought to play a major role in drug biotransformation and the detoxification of xenobiotics. The cytosolic GSH S-transferase...
Saved in:
| Main Author: | |
|---|---|
| Format: | Thesis |
| Language: | English |
| Published: |
Division of Medical Biochemistry and Structural Biology
2018
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867614470975520768 |
|---|---|
| access_status_str | Open Access |
| author | Goold, Richard David |
| author_browse | Goold, Richard David |
| author_facet | Goold, Richard David |
| author_sort | Goold, Richard David |
| collection | Thesis |
| description | The glutathione S-transferases are a group of enzymes which catalyse the conjugation of reduced glutathione with a variety of electrophilic molecules, and they are therefore thought to play a major role in drug biotransformation and the detoxification of xenobiotics. The cytosolic GSH S-transferase isoenzymes of rat, man and mouse have been assigned to three groups, Alpha, Mu and Pi, based on N-terrninal amino acid sequences, substrate specificities, immunological cross-reactivity and sensitivities to inhibitors. The kinetic mechanism of the GSH S-transferases is controversial, due to the observation of non-Michaelian (non-hyperbolic) substrate-rate saturation curves. The most detailed investigations of the steady-state kinetics of glutathione S-transferase have been performed with isoenzyme 3-3 (class Mu) and the substrate 1,2-dichloro-4-nitrobenzene (DCNB). Explanations for the apparently anomalous non-hyperbolic kinetics have included subunit cooperativity, steady-state mechanisms of differing degrees of complexity and the superimposition of either product inhibition or enzyme memory on these mechanisms. This study has confirmed the biphasic kinetics for isoenzyme 3-3 with DCNB and shown non-hyperbolic kinetics for this isoenzyme with 1-chloro-2,4-dinitrobenzene (CDNB) and for isoenzyme 3-4 with DCNB and CDNB. It is proposed that the basic steady-state random sequential Bi Bi mechanism is the simplest mechanism sufficient to explain the non-hyperbolic kinetics of GSH S-transferases 3-3 and 3-4 under initial rate conditions. Neither more complex steady-state mechanisms nor the superimposition of product inhibition or enzyme memory on the simplest steady-state mechanism are necessary. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/27175 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:52:33.918Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| publisher | Division of Medical Biochemistry and Structural Biology |
| publisherStr | Division of Medical Biochemistry and Structural Biology |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/27175 The glutathione S-transferases : kinetics, binding and inhibition Goold, Richard David Medical Biochemistry Glutathione transferase Glutathione transferases Glutathione transferases - Analysis The glutathione S-transferases are a group of enzymes which catalyse the conjugation of reduced glutathione with a variety of electrophilic molecules, and they are therefore thought to play a major role in drug biotransformation and the detoxification of xenobiotics. The cytosolic GSH S-transferase isoenzymes of rat, man and mouse have been assigned to three groups, Alpha, Mu and Pi, based on N-terrninal amino acid sequences, substrate specificities, immunological cross-reactivity and sensitivities to inhibitors. The kinetic mechanism of the GSH S-transferases is controversial, due to the observation of non-Michaelian (non-hyperbolic) substrate-rate saturation curves. The most detailed investigations of the steady-state kinetics of glutathione S-transferase have been performed with isoenzyme 3-3 (class Mu) and the substrate 1,2-dichloro-4-nitrobenzene (DCNB). Explanations for the apparently anomalous non-hyperbolic kinetics have included subunit cooperativity, steady-state mechanisms of differing degrees of complexity and the superimposition of either product inhibition or enzyme memory on these mechanisms. This study has confirmed the biphasic kinetics for isoenzyme 3-3 with DCNB and shown non-hyperbolic kinetics for this isoenzyme with 1-chloro-2,4-dinitrobenzene (CDNB) and for isoenzyme 3-4 with DCNB and CDNB. It is proposed that the basic steady-state random sequential Bi Bi mechanism is the simplest mechanism sufficient to explain the non-hyperbolic kinetics of GSH S-transferases 3-3 and 3-4 under initial rate conditions. Neither more complex steady-state mechanisms nor the superimposition of product inhibition or enzyme memory on the simplest steady-state mechanism are necessary. 2018-01-31T13:47:21Z 2018-01-31T13:47:21Z 1989 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/27175 eng application/pdf Division of Medical Biochemistry and Structural Biology Faculty of Health Sciences University of Cape Town |
| spellingShingle | Medical Biochemistry Glutathione transferase Glutathione transferases Glutathione transferases - Analysis Goold, Richard David The glutathione S-transferases : kinetics, binding and inhibition |
| thesis_degree_str | Doctoral |
| title | The glutathione S-transferases : kinetics, binding and inhibition |
| title_full | The glutathione S-transferases : kinetics, binding and inhibition |
| title_fullStr | The glutathione S-transferases : kinetics, binding and inhibition |
| title_full_unstemmed | The glutathione S-transferases : kinetics, binding and inhibition |
| title_short | The glutathione S-transferases : kinetics, binding and inhibition |
| title_sort | glutathione s transferases kinetics binding and inhibition |
| topic | Medical Biochemistry Glutathione transferase Glutathione transferases Glutathione transferases - Analysis |
| url | http://hdl.handle.net/11427/27175 |
| work_keys_str_mv | AT gooldricharddavid theglutathionestransferaseskineticsbindingandinhibition AT gooldricharddavid glutathionestransferaseskineticsbindingandinhibition |