Comparison of the enzymatic composition of cell-free extracts of non-aflatoxigenicAspergillus parasiticus with respect to late stages of aflatoxin biosynthesis

Abstract

Cell-free extracts of fungal mycelia of two non-aflatoxigenic isolates ofAspergillus parasiticus (SRRC 163 and SRRC 2043) were examined for enzyme activities involved in the latter stages of aflatoxin biosynthesis. Post-microsomal fractions (105 Kxg supernatant) of both SRRC 163 (ATTC 56774) and SRRC 2043 were able to convert sterigmatocystin (ST) toO-methylsterigmatocystin (OMST); whereas the microsomal (105 Kxg pellet) preparation of only SRRC 163 was able to convert OMST to aflatoxin B₁ (AFB₁). A mixture of the microsomal fraction of SRRC 163 and post-microsomal fraction of SRRC 2043 converted ST to AFB₁. Electrophoretic protein separations of the microsomal fractions of the twoA. parasiticus isolates on non-denaturing or denaturing polyacrylamide gel electrophoresis (PAGE) provided equivalent protein profiles.