Figure 4.

Mechanism of the Fe(II)- and 2-OG-dependent dioxygenases including P4H, P3H, and LH hydroxylases. The enzyme active site consists of a ferrous iron ion coordinated by two His residues and one Asp residue. The catalytic reaction consists of several consecutive steps: binding of 2-OG displacing two water molecules; the substrate binding replaces a third water molecule; binding oxygen and forming an anionic intermediate; the formation of a cyclic peroxide molecule by attacks the ketone of 2-OG; the decomposition of intermediate and the formation of the Fe(IV)oxo species; the abstractions of hydrogen from the substrate; and the reaction of substrate radical with the Fe(III)−OH complex to form the hydroxylated substrate.