title: Conversion of 11-hydroxy-O-methylsterigmatocystin to aflatoxin G1 in Aspergillus parasiticus.
abstract: In aflatoxin biosynthesis, aflatoxins G(1) (AFG(1)) and B(1) (AFB(1)) are independently produced from a common precursor, O-methylsterigmatocystin (OMST). Recently, 11-hydroxy-O-methylsterigmatocystin (HOMST) was suggested to be a later precursor involved in the conversion of OMST to AFB(1), and conversion of HOMST to AFB(1) was catalyzed by OrdA enzyme. However, the involvement of HOMST in AFG(1) formation has not been determined. In this work, HOMST was prepared by incubating OrdA-expressing yeast with OMST. Feeding Aspergillus parasiticus with HOMST allowed production of AFG(1) as well as AFB(1). In cell-free systems, HOMST was converted to AFG(1) when the microsomal fraction, the cytosolic fraction from A. parasiticus, and yeast expressing A. parasiticus OrdA were added. These results demonstrated (1) HOMST is produced from OMST by OrdA, (2) HOMST is a precursor of AFG(1) as well as AFB(1), and (3) three enzymes, OrdA, CypA, and NadA, and possibly other unknown enzymes are involved in conversion of HOMST to AFG(1).
authors.affiliation: National Food Research Institute, National Agricultural Research Organization (NARO), Tsukuba, Ibaraki 305-8642, Japan.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Zeng
authors.forename: Hidemi
authors.initials: H
authors.lastname: Hatabayashi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakagawa
authors.forename: Jingjing
authors.initials: J
authors.lastname: Cai
authors.forename: Ryoya
authors.initials: R
authors.lastname: Suzuki
authors.forename: Emi
authors.initials: E
authors.lastname: Sakuno
authors.forename: Toshitsugu
authors.initials: T
authors.lastname: Tanaka
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ito
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Ehrlich
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Nakajima
authors.forename: Kimiko
authors.initials: K
authors.lastname: Yabe
mesh_terms: D000348:Aflatoxins / Q000096:biosynthesis*; D001230:Aspergillus / Q000201:enzymology*; D002474:Cell-Free System / Q000378:metabolism; D005656:Fungal Proteins; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005810:Multigene Family; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013241:Sterigmatocystin / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C460120:11-hydroxyl O-methylsterigmatocystin; D000348:Aflatoxins; D005656:Fungal Proteins; D013241:Sterigmatocystin; C027955:aflatoxin G1