Fig. 2: Plausible reaction mechanisms account for Fe/2OG enzyme-catalyzed hydroxylation and desaturation.

A Canonical hydroxylation is initiated by an Fe(IV)-oxo species triggered hydrogen atom transfer (HAT). It is then followed by oxygen-rebound to complete hydroxylation. The HAT site and Fe(IV)-oxo are highlighted in blue and red, respectively. B In the Fe/2OG enzymes, i.e., PIsnB and PvcB, catalyzed desaturation reactions using 4 as the substrate, following HAT step, a hydroxylated intermediate or a benzylic cation may serve as a common species to afford 2 and 3 via deprotonation (pathway a, blue arrow) and decarboxylation (pathway b, red arrow), respectively. Other alternative mechanisms are summarized in the supplementary information (Supplementary Fig. 23).