<p>FO synthase catalyzes the radical-mediated transfer of the hydroxybenzyl group from 4-hydroxyphenylpyruvate (HPP) to 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione to form 7,8-didemethyl-8-hydroxy-5-deazariboflavin (FO) [<cite idref="PUB00045884"/>]. This entry represents CofH/subunit 2 of FO synthase and other related radical SAM proteins.</p>