ENZYMATIC CONVERSION OF STERIGMATOCYSTIN INTO AFLATOXIN-B1 BY CELL-FREE-EXTRACTS OF ASPERGILLUS-PARASITICUS

A cell-free extract, prepared from A. parasiticus ATCC 15517 grown in synthetic medium, was active in converting [14C]sterigmatocystin into the carcinogen aflatoxin B1 in the presence of NADPH. The activity was demonstrated by the time course of conversion and the linear dependence of the yield of product on enzyme concentrations. Optimum activity was obtained at pH 7.5-7.8 at 27.degree. C. The results confirm sterigmatocystin as a biogenetic precursor of aflatoxin B1. Techniques were developed for enzymatic studies on alfatoxin biosynthesis.