Recent developments in enzymatic chlorination.

While the existence of chlorinated natural products has been known for over 100 years, our understanding of the enzymology of biological chlorination reactions has been limited to chloroperoxidases, which are now known not to play a significant role in chlorometabolite biosynthesis. The discoveries of new classes of halogenases, described in this Highlight, have shed new light on the mechanisms of enzymatic chlorination of aromatic and aliphatic compounds.