Reversible covalent inhibition of a phenol sulfotransferase by coenzyme A
- 作者：Sundari Chodavarapu ; Heather Hertema ; Tien Huynh ; Jessica Odette ; Rachel Miller ; Aaron Fullerton ; Jason Alkirwi ; D’ ; Juan Hartsfield ; Kaillathe Padmanabhan ; Caleb Woods ; et al.
- 关键词：Sulfotransferase ; SULT1A1 ; Inhibition ; Inactivation ; Kinetics ; CoA ; Regulation ; Model ; Induced fit
- 刊名：Archives of Biochemistry and Biophysics
- 出版年：2007
- 期刊代码：116_00039861
- 类别：ch
- 出版时间：15 January 2007
- 卷：457
- 期：2
- 页码：197-204
- 文件大小：568 K
摘要
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 ;c;M and an inactivation rate constant of 0.07 min<sup>−1sup>. 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.