Biosynthetic Studies of Fumonisin B₁ and AAL Toxins

Abstract

The biosynthesis of the sphinganine analogue mycotoxins (SAMs) fumonisin B1 and the AAL toxins was studied by growing Fusarium moniliforme and Alternaria alternata f. sp. lycopersici in liquid culture. Radioactive and stable isotopically labeled amino acid, water, and molecular oxygen precursors were added to the culture media and toxins were analyzed using thin-layer chromatography, liquid scintillation counting, high-performance liquid chromatography (HPLC), 13C nuclear magnetic resonance (NMR) spectroscopy, and electrospray mass spectrometry (ESMS). Results indicated that glycine was incorporated directly into the AAL toxins and that methionine was incorporated into the AAL toxin methyl groups. Oxygens in tricarballylic acid moieties for fumonisin B1 and the AAL toxins were derived from H2O while the lipid backbone hydroxyls for fumonisin B1 and the AAL toxins originated from molecular oxygen. Isotopic enrichment patterns for the various AAL toxins showed marked differences among toxins, suggesting a complex, rather than sequential, biosynthetic pattern. Keywords: Mycotoxins; sphinganine analogue mycotoxins; isotope enrichment

A Polyketide Synthase Gene Required for Biosynthesis of Fumonisin Mycotoxins in Gibberella fujikuroi Mating Population A

“…However, the putative polyketide synthesized by Fum5p is probably a completely saturated, 18-carbon molecule resembling or identical to the fatty acid stearate. This is evident from sequence data, which indicate that Fum5p has all three functional domains (KR, DH, and ER) required to fully reduce ␤-carbonyls to saturated carbons, and from precursor feeding studies, which indicate that the oxygen atoms attached to the fumonisin backbone are derived from molecular oxygen rather than from ␤-carbonyl oxygens (Caldas et al, 1998). As far as we are aware, fumonisins are the first example of a fungal polyketide synthesized by removing all oxygens from ␤-carbonyl carbons during formation of the polyketide chain and then later reoxygenating some of these same carbons, presumably by oxygenases after synthesis of the chain is complete.…”

“…Feeding studies with a variety of precursors indicate that different components of the FB 1 molecule have diverse biogenic origins. Specifically, the oxygen atoms at C-3, C-5, C-10, C-14, and C-15 are derived from molecular oxygen (Caldas et al, 1998), the tricarballylic moieties at C-14 and C-15 may be derived from glutamic acid via the citric acid cycle (Blackwell et al, 1996), the methyl groups at C-12 and C-16 are derived from methionine , the amino group and C-1 and C-2 of the fumonisin backbone are derived from alanine (Branham and Plattner, 1993), and C-3 to C-20 of the backbone are derived from acetate (Blackwell et al, 1994).…”

Impacto das Fumonisinas, Aflatoxinas e Ocratoxina A na Avicultura

“…Os carbonos 3-20 são derivados do acetato, os grupos aminos em C-1 e C-2 da alanina (BLACKWELL et al, 1996;BRANHAM;PLATTNER, 1993), e os dois grupamentos metil nos carbonos 12 e 16 da metionina (PLATTNER; . O grupo hidroxila no C-3 é proveniente do grupo carbonila derivado do acetato, enquanto que os grupos hidroxila nos carbonos 5, 10, 14 e 15 são originados do oxigênio molecular (CALDAS et al, 1998 tricarboxílicos provavelmente são derivados do ácido glutâmico pela via do ciclo do ácido cítrico (ex. ácido aconítico) (BLACKWELL et al, 1996).…”

Functional replacement of the ketosynthase domain of FUM1 for the biosynthesis of fumonisins, a group of fungal reduced polyketides

“…YPD medium and V-8 juice agar were respectively used to produce mycelia and conidia [21], and cracked maize kernels (CMK) for fumonisin production [7,21].…”

“…The two methyl groups at C-12 and C-16 are derived from methionine [19]. The hydroxyl oxygen on C-5, C-10, C-14, and C-15 of fumonisin B 1 (FB 1 ) are derived from molecular oxygen, whereas the hydroxyl oxygen on C-3 is from the carbonyl group of acetate [7]. A cluster of 15 genes (FUM) for fumonisin biosynthesis has been cloned from F. verticillioides [20,21,24], among which is a PKS gene (FUM1).…”