Aflatoxins pathway

Initial attempts to purify enzymes from A, parasiticus mycelial extracts that catalyze aflatoxin synthesis were unsuccessful because these enzymes are present in relatively low concentrations and are extremely short-lived (23). Subsequently, several techiuques were examined for disruption of large quantities of mycelia to obtain active and stable cell-fiee preparations (23, 24) pertinent enzymes were recovered from cell-free extracts after grinding mycelia under liquid nitrogen (24). The optimum age of mycelial cultures for recovery of aflatoxin pathway enzymes was determined to be between 72 and 84 h (24a, 25). 

Townsend CA Progress towards a biosynthetic rationale of the aflatoxin pathway. Pure Appl Chem 1997 58 227-238. 

Yu J, Chang PK, Cary JW, Wright M, Bhatnagar D, Cleveland TE, Payne GA, Linz JE Comparative mapping of aflatoxin pathway gene cluster in Aspergillus parasiticus and Aspergillus flams. Appl Environ Microbiol 1995 61 2365-2371. 

TOWNSEND, C.A., CHRISTENSEN, S.B., Stable isotope studies of anthraquinone intermediates in the aflatoxin pathway. Tetrahedron, 1983, 39, 3575-3582. 

CHANG, P.K., The A.spergillus parasiticus protein AFLJ interacts with the aflatoxin pathway-specific regulator AFLR, Mol Genet. Genomics, 2003, 268, 711-719. 

The aflatoxin pathway is one of the best-studied pathways of fungal secondary metabolism. Attempts to decipher the pathway began with the discovery of the structure of these toxins. However, the major biochemical steps and the corresponding genetic components of AFBi biosynthesis have been elucidated at a molecular level only in the last decade. Significant progress has been made in deciphering the details of the aflatoxin/ST biosynthetic pathways. " " " " ... 

Several specific enzyme activities associated with precursor conversions in the aflatoxin pathway " " have been partially purified (Fig.l 1.1) whereas others such as methyltransferases " have been purified to homogeneity. Several other enzymes involved in aflatoxin biosynthesis, such as a reductase and a cyclase, " have also been purified from A. parasiticus. A desaturase that converts VERA to VERB has been found in cell-free fungal extracts. Matsushima et al. have purified and characterized two versiconal hemiacetal acetate reductases involved in toxin synthesis, whereas Kusumoto and Hsieh purified to homogeneity an esterase that converts VHA to versiconal. ... 

TRAIL, F., MAHANTI, N., RARICK, M., MEHIGH, R., LIANG, S.H., ZHOU, R., LINZ, J.E., Physical and transcriptional map of an aflatoxin gene cluster in Aspergillus parasiticus and functional disruption of a gene involved early in the aflatoxin pathway, Appl. Environ. Microbiol., 1995, 61,2665-2673. 

EHRLICH, K.C., MONTALBANO, B.G., CARY, J.W., Binding of the C6-zinc cluster protein, AFLR, to the promoters of aflatoxin pathway biosynthesis genes in Aspergillus parasiticus. Gene, 1999,230,249-257. 

CHANG P.-K., YU, J., BHATNAGAR, D., CLEVELAND, T.E., The carboxy-terminal portion of the aflatoxin pathway regulatory protein AFLR of A.spergillus parasiticus activates GALldacZ gene expression in Saccharomyces cerevisiae, Appl. Environ. Microbiol., 1999,65,2058-2512. 

---