Enzyme reactions and genes in aflatoxin biosynthesis

Abstract

Aflatoxins are highly toxic and carcinogenic substances mainly produced by Aspergillus flavus and Aspergillus parasiticus. Sterigmatocystin is a penultimate precursor of aflatoxins and also a toxic and carcinogenic substance produced by many species, including Aspergillus nidulans. Recently, the majority of the enzyme reactions involved in aflatoxin/sterigmatocystin biosynthesis have been clarified, and the genes encoding the enzymes have been isolated. Most of the genes constitute a large gene cluster in the fungal genome, and their expression is mostly regulated by a product of the regulatory gene aflR. This review will summarize the enzymatic steps and the genes in aflatoxin/sterigmatocystin biosynthesis.

A Fungal Family of Transcriptional Regulators: the Zinc Cluster Proteins

“…Aflatoxins are secondary metabolites produced by several Aspergillus species. These compounds are (292). Indeed, epidemiological studies have established that aflatoxin exposure is a major risk factor for liver cancer (292).…”

The occurrence of aflatoxin B1 contamination in peanuts and peanut products marketed in southern Brazil

“…In the European Union, for example, the maximum levels allowed in food for AFB1 and for the sum of aflatoxins are 2.0 µg/kg and 4.0 µg/kg, respectively (Koe 1999). It is highly unlikely that commodities will contain aflatoxins B 2 , G 1 and G 2 and not AFB1 (Yabe and Nakajima, 2004), and the concentration of the sum of aflatoxins B 2 , G 1 and G 2 is generally less than the concentration of AFB1 alone. For this reason, analysis of one target component (AFB1) appears to be sufficient, efficient, and more practical (FAO 2004).…”

A new role for coenzyme F420 in aflatoxin reduction by soil mycobacteria

“…Aspergillus flavus and Aspergillus parasiticus produce these furanocoumarin toxins in microsomes through a polyketide biosynthetic pathway requiring more than 20 enzymes (Yabe and Nakajima, 2004). The blue-green fluorescent aflatoxins can be readily detected, yet their environmental fate and mode of degradation are unknown.…”

“…1). If infected corn is used for alcoholic fermentation in biofuel plants, mycotoxins could be concentrated in distillers' grain fed to livestock (Wu and Munkvold, 2008); however, aflatoxin levels were generally low in a recent survey of corn co-products (Zhang et al, 2009).Aspergillus flavus and Aspergillus parasiticus produce these furanocoumarin toxins in microsomes through a polyketide biosynthetic pathway requiring more than 20 enzymes (Yabe and Nakajima, 2004). The blue-green fluorescent aflatoxins can be readily detected, yet their environmental fate and mode of degradation are unknown.…”