8erb

Structural highlights

Function

FUB7_GIBF5 Sulfhydrylase; part of the gene cluster that mediates the biosynthesis of fusaric acid, a mycotoxin with low to moderate toxicity to animals and humans, but with high phytotoxic properties (PubMed:26662839). L-aspartate is suggested as fusaric acid amino acid precursor that is activated and further processed to O-acetyl-L-homoserine by cluster enzymes aspartate kinase FUB3 and homoserine O-acetyltransferase FUB5, as well as enzymes of the primary metabolism (PubMed:26662839). The polyketide synthase (PKS) FUB1 generates the triketide trans-2-hexenal which is presumptively released by the hydrolase FUB4 and linked to the NRPS-bound amino acid precursor by NAD(P)-dependent dehydrogenase FUB6 (PubMed:26662839). FUB1, FUB4, and the non-canonical NRPS Fub8 may form an enzyme complex (PubMed:26662839). Further processing of the NRPS-bound intermediate might be carried out by FUB6 and the O-acetylhomoserine FUB7, enabling a spontaneous electrocyclization to close the carbon backbone of fusaric acid (PubMed:26662839). Dihydrofusaric acid is likely to be released via reduction by the thioester reductase (TR) domain of FUB8 whereupon the final oxidation to fusaric acid may (also) be performed by the FMN-dependent dehydrogenase FUB9 (PubMed:26662839).^[1]

References

1. ↑ Studt L, Janevska S, Niehaus EM, Burkhardt I, Arndt B, Sieber CM, Humpf HU, Dickschat JS, Tudzynski B. Two separate key enzymes and two pathway-specific transcription factors are involved in fusaric acid biosynthesis in Fusarium fujikuroi. Environ Microbiol. 2016 Mar;18(3):936-56. PMID:26662839 doi:10.1111/1462-2920.13150