title: Versicolorin A hemiacetal, hydroxydihydrosterigmatocystin, and aflatoxin G2 alpha reductase activity in extracts from Aspergillus parasiticus.
abstract: Versicolorin A hemiacetal was converted to versicolorin C in cell-free systems from Aspergillus parasiticus. The rate of reaction catalyzed by the 35-70% ammonium sulfate fraction was 0.43 nmol min-1 mg-1 with NADPH as cosubstrate and 0.17 nmol min-1 mg-1 with NADH at 25 degrees C at pH 7.4. The product from incubation of 17-hydroxy-16,17-dihydrosterigmatocystin with the 35-70% ammonium sulfate fraction and NADPH was a polar compound which was converted to dihydrosterigmatocystin by 0.4 M HCl. The polar compound is proposed to be the 14,17-hydrated open-chain derivative of dihydrosterigmatocystin. Aflatoxin G2 alpha was also reduced in this system to a polar product tentatively identified as the 13,16-hydrated open-chain derivative of AFG2. The reductase activity may be involved in the formation of reduced intermediates and aflatoxins in cultures of A. parasiticus.
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University, Lubbock 79409-1061.
authors.forename: J A
authors.initials: JA
authors.lastname: Anderson
authors.forename: C H
authors.initials: CH
authors.lastname: Chung
authors.forename: S H
authors.initials: SH
authors.lastname: Cho
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000880:Anthraquinones / Q000378:metabolism*; D001230:Aspergillus / Q000201:enzymology / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D013241:Sterigmatocystin / Q000031:analogs & derivatives* / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D000880:Anthraquinones; D009243:NAD; D013241:Sterigmatocystin; C066393:17-hydroxy-16,17-dihydrosterigmatocystin; D009249:NADP; C066394:versicolorin A hemiacetal; D000429:Alcohol Oxidoreductases; C066395:aflatoxin G2a reductase