Requirement of monooxygenase-mediated steps for sterigmatocystin biosynthesis by Aspergillus nidulans.
Sterigmatocystin (ST) and aflatoxin B(1) (AFB(1)) are two polyketide-derived Aspergillus mycotoxins synthesized by functionally identical sets of enzymes. ST, the compound produced by Aspergillus nidulans, is a late intermediate in the AFB(1) pathway of A. parasiticus and A. flavus. Previous biochemical studies predicted that five oxygenase steps are required for the formation of ST. A 60-kb ST gene cluster in A. nidulans contains five genes, stcB, stcF, stcL, stcS, and stcW, encoding putative monooxygenase activities. Prior research showed that stcL and stcS mutants accumulated versicolorins B and A, respectively. We now show that strains disrupted at stcF, encoding a P-450 monooxygenase similar to A. parasiticus avnA, accumulate averantin. Disruption of either StcB (a putative P-450 monooxygenase) or StcW (a putative flavin-requiring monooxygenase) led to the accumulation of averufin as determined by radiolabeled feeding and extraction studies.
Keller
N P
NP
Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas 77843, USA. n-keller@tamu.edu
Watanabe
C M
CM
Kelkar
H S
HS
Adams
T H
TH
Townsend
C A
CA
D000880:Anthraquinones / Q000378:metabolism; D001233:Aspergillus nidulans / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D010105:Oxygenases / Q000235:genetics* / Q000378:metabolism*; D013241:Sterigmatocystin / Q000096:biosynthesis*; D014170:Transformation, Genetic
D000880:Anthraquinones; D013241:Sterigmatocystin; C024820:averantin; C029856:averufin; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming); C002754:norsolorinic acid