Are the genes nadA and norB involved in formation of aflatoxin G(1)?
Aflatoxins, the most toxic and carcinogenic family of fungal secondary metabolites, are frequent contaminants of foods intended for human consumption. Previous studies showed that formation of G-group aflatoxins (AFs) from O-methylsterigmatocystin (OMST) by certain Aspergillus species involves oxidation by the cytochrome P450 monooxygenases, OrdA (AflQ) and CypA (AflU). However, some of the steps in the conversion have not yet been fully defined. Extracts of Aspergillus parasiticus disruption mutants of the OYE-FMN binding domain reductase-encoding gene nadA (aflY) contained a 386 Da AFG(1) precursor. A compound with this mass was predicted as the product of sequential OrdA and CypA oxidation of OMST. Increased amounts of a 362 Da alcohol, the presumptive product of NadA reduction, accumulate in extracts of fungi with disrupted aryl alcohol dehydrogenase-encoding gene norB. These results show that biosynthesis of AFG(1) involves NadA reduction and NorB oxidation.
Ehrlich
Kenneth C
KC
Southern Regional Research Center, 1100 Robert E. Lee Blvd, P.O. Box 19687, New Orleans, LA 70179, USA.
Scharfenstein
Leslie L
LL
Southern Regional Research Center, 1100 Robert E. Lee Blvd, P.O. Box 19687, New Orleans, LA 70179, USA.
Montalbano
Beverly G
BG
Southern Regional Research Center, 1100 Robert E. Lee Blvd, P.O. Box 19687, New Orleans, LA 70179, USA.
Chang
Perng-Kuang
PK
Southern Regional Research Center, 1100 Robert E. Lee Blvd, P.O. Box 19687, New Orleans, LA 70179, USA.