Abstract
Desaturase activity that converts versicolorin B (VB) to versicolorin A (VA) was detected in the presence of NADPH in the microsomal fraction of Aspergillus parasiticus NIAH-26, which endogenously produced neither aflatoxins nor anthraquinone- or xanthone-precursors in a yeast-extract sucrose (YES) medium. A smaller amount of VA was also produced from versicolorin C (VC). When the same mold was cultured with VA in YES medium in feeding experiments, aflatoxins B1 (AFB1) and G1 (AFG1) were produced. When either VB or VC was fed to the mold, aflatoxins B2 (AFB2) and G2 (AFG2) as well as AFB1 and AFG1 were produced. These results indicate that the branching step between AFB1•AFG1 and AFB2•AFG2 corresponds to the desaturation reaction from VB to VA.
