FAD-linked oxidoreductase; part of the gene cluster that mediates the biosynthesis of isofumigaclavines, fungal ergot alkaloids (PubMed:28620689). The tryptophan dimethylallyltransferase ifgA catalyzes the first step of ergot alkaloid biosynthesis by condensing dimethylallyl diphosphate (DMAP) and tryptophan to form 4-dimethylallyl-L-tryptophan (PubMed:28620689). The second step is catalyzed by the methyltransferase ifgB that methylates 4-dimethylallyl-L-tryptophan in the presence of S-adenosyl-L-methionine, resulting in the formation of N-methyl-dimethylallyl-L-tryptophan (PubMed:28620689). The catalase ifgD and the FAD-dependent oxidoreductase ifgC then transform N-methyl-dimethylallyl-L-tryptophan to chanoclavine-I which is further oxidized by ifgE in the presence of NAD(+), resulting in the formation of chanoclavine-I aldehyde (PubMed:28902217). The chanoclavine-I aldehyde reductases ifgG and/or fgaOx3 reduce chanoclavine-I aldehyde to dihydrochanoclavine-I aldehyde that spontaneously dehydrates to form 6,8-dimethyl-6,7-didehydroergoline (PubMed:28620689, PubMed:28902217). The festuclavine dehydrogenases ifgF1 and/or ifgF2 then catalyze the reduction of 6,8-dimethyl-6,7-didehydroergoline to form festuclavine (PubMed:28620689). Hydrolysis of festuclavine by a yet undetermined cytochrome P450 monooxygenase (called ifgH) then leads to the formation of isofumigaclavine B which is in turn acetylated by ifgI to isofumigaclavine A (PubMed:28620689). Penicillium roqueforti has interestingly at least two sets of genes for the consumption of chanoclavine-I aldehyde on three different loci, the OYEs ifgG/fgaOx3 and the festuclavine synthase homologs ifgF1/ifgF2 (PubMed:28620689, PubMed:28902217). The reason for the duplication of these genes is unclear, probably to ensure the conversion of chanoclavine-I aldehyde by differential gene expression under various environmental conditions (PubMed:28902217). Alkaloid biosynthesis; ergot alkaloid biosynthesis. Belongs to the oxygen-dependent FAD-linked oxidoreductase family.