ABSTRACT
Sulfate conjugates are usually less stable than glucuronide conjugates of the same substrate because sulfate is a better leaving group than glucuronate. Some of the sulfate conjugates are so labile under physiological conditions that their formation in vivo, if it occurs, cannot be detected. The chemical mechanism for the generation of reactive intermediates from sulfate conjugates seems to be the loss of the sulfate group, resulting in nitrenium ion or carbonium ion resonance forms. Alternatively, 4-nitrophenyl sulfate may be used as the donor of the sulfate group for sulfation, in which case the rate of generation of frees 4-nitrophenol indicates the rate of sulfation. Low-molecular weight compounds like methionine may compete effectively with RNA or protein for trapping reactive intermediates.
