Oxidoreductase; part of the gene cluster that mediates the biosynthesis of hydroxamate-containing siderophores that play a critical role in virulence via intracellular iron acquisition during macrophage infection (PubMed:18404210). Binds 6-hydroxy-FAD non-covalently. Siderophore biosynthesis. Expression is induced during iron deprivation and is regulated by the transcription factor SRE1 (PubMed:18404210, PubMed:22117028). Belongs to the FAD-dependent oxidoreductase family.