Control of Activity through Oxidative Modification at the Conserved Residue Cys66 of Aryl Sulfotransferase IV

摘要: Oxidation at Cys66 of rat liver aryl sulfotransferase IV alters the enzyme's catalytic activity, pH optima and substrate specificity. Although this is a cytosolic detoxication enzyme, optimum for standard assay 4-nitrophenol 5.5; upon oxidation, changes to physiological range. The principal effect change in activation, which manifest by an increase K′cat without any major influence on binding. In contrast, with tyrosine methyl ester as substrate, activity occurs 8.0; it ceases be pH. presence was essential activation occur, thereby providing putative reason underlying conserved nature cysteine throughout phenol family. Mapping disulfides mass spectrometry showed critical event oxidation form disulfide either Cys232 or glutathione, one effective. These results point mechanism regulating key enzyme xenobiotic during cellular oxidative stress.