Reversible covalent inhibition of a phenol sulfotransferase by coenzyme A
| Autor: | Jason Alkirwi, Heather Hertema, Jessica Odette, Kaillathe Padmanabhan, Sundari Chodavarapu, D’Juan Hartsfield, Joe D. Beckmann, Tien Huynh, Aaron M. Fullerton, Caleb Woods, Rachel Miller |
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| Rok vydání: | 2006 |
| Předmět: |
Models
Molecular Sulfotransferase Stereochemistry Coenzyme A Biophysics Sulfides Biochemistry Chemical kinetics chemistry.chemical_compound Enzyme activator Reaction rate constant Animals Cysteine Molecular Biology Mercaptoethanol Substrate (chemistry) Hydrogen-Ion Concentration Arylsulfotransferase Dissociation constant Enzyme Activation Kinetics chemistry Mutation Cattle |
| Zdroj: | Archives of biochemistry and biophysics. 457(2) |
| ISSN: | 0003-9861 |
| Popis: | Phenol sulfotransferases (SULTs), which normally bind 3'-phosphoadenosine-5'-phosphosulfate as the donor substrate, are inhibited by CoA and its thioesters. Here, we report that inhibition of bovine SULT1A1 by CoA is time-dependent at neutral pH under non-reducing conditions. The rates of inactivation by CoA indicate an initial reversible SULT:CoA complex with a dissociation constant of 5.7 microM and an inactivation rate constant of 0.07 min(-1). Titrations with CoA and prolonged incubations reveal that inactivation of the dimeric enzyme is stoichiometric, consistent with the observation of complete conversion of the protein to a slightly decreased electrophoretic mobility. Both activity and normal electrophoretic migration are restored by 2-mercaptoethanol. Mutagenesis demonstrated that Cys168 is the site of CoA adduction, and a consistent model was constructed that reveals a new SULT molecular dynamic. Cysteine reaction kinetics with Ellman's reagent revealed a PAPS-induced structural change consistent with the model that accounts for binding of CoA. |
| Databáze: | OpenAIRE |
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