Bhatnagar D, Cleveland T E, Lillehoj E B
Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, LA 70124.
Mycopathologia. 1989 Sep;107(2-3):75-83. doi: 10.1007/BF00707542.
Recent work on the aflatoxin biosynthetic pathway is reviewed, with special emphasis on the enzymes of the late stages of the pathway involving conversion of sterigmatocystin (ST) to aflatoxin B1 (AFB1) through an O-methylsterigmatocystin intermediate. Two enzyme activities were discovered in subcellular fractions of cell-free extracts of a mutant strain of Aspergillus parasiticus (SRRC 163): 1) A post-microsomal methyltransferase (MT) catalyzed conversion of ST to OMST, and 2) a microsomal-associated activity (oxido-reductase) converted OMST to AFB1. The 168 KDa, anionic MT was purified to homogeneity and characterized (two subunits, 110 KDa and 58 KDa). Preliminary evidence indicated the presence of a cationic isozyme of the MT in mycelial extracts. The oxido-reductase has been partially purified and characterized. Polyclonal antibodies were prepared to the anionic MT and the enzyme's amino acid composition determined. A cDNA library has been constructed from mRNA isolated from Aspergillus parasiticus mycelia during the onset of AFB1 biosynthesis for the purpose of identifying the genes responsible for aflatoxin biosynthesis.
本文综述了黄曲霉毒素生物合成途径的近期研究工作，特别强调了该途径后期的酶，这些酶涉及通过O-甲基柄曲霉素中间体将柄曲霉素（ST）转化为黄曲霉毒素B1（AFB1）。在寄生曲霉突变株（SRRC 163）的无细胞提取物的亚细胞组分中发现了两种酶活性：1）微粒体后甲基转移酶（MT）催化ST转化为OMST，2）微粒体相关活性（氧化还原酶）将OMST转化为AFB1。168 kDa的阴离子MT被纯化至同质并进行了表征（两个亚基，110 kDa和58 kDa）。初步证据表明在菌丝体提取物中存在MT的阳离子同工酶。氧化还原酶已被部分纯化并进行了表征。制备了针对阴离子MT的多克隆抗体并测定了该酶的氨基酸组成。为了鉴定负责黄曲霉毒素生物合成的基因，已从黄曲霉毒素生物合成开始时从寄生曲霉菌丝体中分离的mRNA构建了一个cDNA文库。
