Again benzene serves us as a good example. Also similar to the Cytochrome P-450 enzymes, the enzymes which catalyze the phase II reactions are present in virtually every organism. Generally the Phase II reactions are designed to bioinactivate xenobiotics however there are a few notable exceptions where the more water soluble compound is more bioactive than its parent compound. The formation of glucuronides is quantitatively the most important. However the conjugation of a polar group with glucuronic acid can only occur after the glucuronic acid has been activated.
II reaction is sulfate conjugation.
As with glucuronic acid, the sulfate needs to be activated before the reaction with the substrate can take place. Glutathione conjugation eventually results in the formation of Mercapturic acids. These reactions take place with a wide variety of substances, which often have a reactive group, such as a halogen atom. Examples are the conjugations of dichloronitrobenzene and bromocyclohexane with glutathione. These substances eventually form mercapturic acids and are excreted.