Fig. 5.

Proposed biosynthesis of aflavarin. The PKS AfvB assembles 4,7-didesmethyl-siderin from an acyl started unit and four malonyl units. AfvC can perform subsequent methylations affording siderin. Hydroxylation by AfvA gives hydroxy-siderin, which can be oxidatively coupled with siderin by the AfvE P450 to form aflavarin. An alternate pathway to aflavarin is possible by an AfvE-catalyzed coupling of hydroxydesmethyl-siderin and siderin followed by a methylation of desmethylaflavarin by AfvD. Adapted from Cary et al.²⁹⁾.