Anderson JA, Chung CH, Cho SH.
Versicolorin A hemiacetal, hydroxydihydrosterigmatocystin,
and aflatoxin G2 alpha reductase activity in extracts from
Department of Chemistry and Biochemistry, Texas Tech
University, Lubbock 79409-1061.
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.