Hydroxyornithine transacylase; part of the siderophore biosynthetic pathway (PubMed:17845073, PubMed:23617799). Aspergillus fumigatus produces 4 types of siderophores, low-molecular-mass iron chelators, including excreted fusarinine C (FsC) and triacetylfusarinine C (TAFC) for iron uptake and intacellular ferricrocin (FC) for hyphal and hydroxyferricrocin (HFC) for conidial iron distribution and storage. TAFC consists of 3 N(2)-acetyl-N(5)-anhydromevalonyl-N(5)-hydroxyornithine residues cyclically linked by ester bonds; FC is a cyclic hexapeptide with the structure Gly-Ser-Gly-(N(5)-acetyl-N(5)-hydroxyornithine)x3. The biosynthesis of all four siderophores depends on the hydroxylation of ornithine, catalyzed by the monooxygenase sidA (PubMed:15504822, PubMed:16113265). Subsequently, the pathways for biosynthesis of extra- and intracellular siderophores split (PubMed:17845073). For biosynthesis of extracellular siderophores, the transacylase sidF transfers anhydromevalonyl to N(5)-hydroxyornithine (PubMed:17845073). The required anhydromevalonyl-CoA moiety is derived from mevalonate by CoA ligation and dehydration catalyzed by sidI and sidH respectively (PubMed:22106303). The acetylation of N(5)-hydroxyornithine for FC biosynthesis involves the constitutively expressed sidL (PubMed:21622789). FC is hydroxylated to HFC by an as yet uncharacterized enzyme during conidiation (PubMed:17845073). Assembly of fusarinine C (FsC) and FC is catalyzed by two different nonribosomal peptide synthetases (NRPS), sidD and sidC respectively (PubMed:17845073). Subsequently, sidG catalyzes N2-acetylation of FsC for forming TAFC (PubMed:17845073). Both extra- and intracellular siderophores are crucial for growth during iron limitation and virulence (PubMed:16113265).