Phase II Enzymes

Abstract

Functionalization reaction catalyzed by a phase I enzyme incorporates a functional group to a foreign compound, resulting in the formation of an intermediate metabolite. Many intermediates contain highly reactive chemical groups, which have the potential to react with cellular components (proteins, lipids, and DNA). The continuous presence of chemically active intermediates can lead to adverse health effects and various disease conditions. In detoxification process, intermediate metabolites undergo phase II metabolism to form highly hydrophilic and less reactive compounds, facilitating their excretion from the body through urine or bile. A foreign compound that already possesses a functional group can bypass phase I metabolism and directly take part in phase II metabolism before being eliminated from the body. Unlike phase I enzymes serving for activation metabolism, phase II enzymes deactivate and detoxify foreign compounds and are referred to as detoxification enzymes.