Isolation and characterization of Aspergillus parasiticus mutants with impaired aflatoxin production by a novel tip culture method

Yabe, Kimiko; Nakamura, Hitomi; Ando, Y; Terakado, Nobuaki; Nakajima, Hiromitsu; Hamasaki, Takashi

doi:10.1128/aem.54.8.2096-2100.1988

Cited by 60 publications

(34 citation statements)

References 26 publications

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“…A. parasiticus NIAH-26, a UV-irradiated mutant of A. parasiticus SYS-4 (NRRL-2999), was mainly used. NIAH-26 produced neither aflatoxins nor precursors (24). A wild strain, A. oryzae SYS-2 (IFO 4251), was also used, as it produces neither aflatoxins nor their precursors.…”

Section: Methodsmentioning

confidence: 99%

Enzymatic conversion of norsolorinic acid to averufin in aflatoxin biosynthesis

Yabe

Nakamura

Nakajima

et al. 1991

Appl Environ Microbiol

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Hydroxyaverantin (HAVN) was isolated from a mold, Emericella heterothallica IFO 30842. Aspergillus parasiticus NIAH-26, a UV-irradiated mutant of A. parasiticus SYS-4, produced neither aflatoxins nor precursors in yeast extract-sucrose (YES) medium. When the postmicrosome (cytosol) fraction of NIAH-26, which had been prepared from the culture in YES medium, was incubated with norsolorinic acid (NA) in the presence of NADH or NADPH, averantin (AVN) was produced. The reverse reaction from AVN to NA was promoted by the addition of NAD or NADP (dehydrogenase reaction). When the microsome fraction of NIAH-26 was incubated with AVN, HAVN was produced in the presence of NADPH (monooxygenase reaction). HAVN was, furthermore, oxidized to averufin (AVR) by the cytosol fraction of NIAH-26 in the presence of NAD or NADP (dehydrogenase reaction). In the feeding experiments with A. parasiticus NIAH-26, aflatoxins were produced from AVN, HAVN, NA, and AVR but not from averufanin or averythrin. These results indicate that the reaction sequence NA<-*AVN-*HAVN-*AVR is involved in the biosynthetic pathway of aflatoxins. The enzyme activities described here were dependent on the culture medium, and no enzyme activities were observed in the nonaflatoxigenic strain A. oryzae SYS-2 (IFO 4251).

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Section: Methodsmentioning

confidence: 99%

Enzymatic conversion of norsolorinic acid to averufin in aflatoxin biosynthesis

Yabe

Nakamura

Nakajima

et al. 1991

Appl Environ Microbiol

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“…In this sense, we obtained more suitable results with UV light, with values around 1 % in many experiments. With UV light, different authors obtained results of survival percentage between 1-5 % in those fungi species (3,6,8,13,14).…”

Section: Resultsmentioning

confidence: 99%

Comparison of the Use of UV Light and Nitrosoguanidine as Mutagenic Treatments in Aspergillus parasiticus

García

Suárez

1993

Journal of Veterinary Medicine, Series B

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“…A. parasiticus NIAH-26, a UV-irradiated mutant of A. parasiticus SYS-4 (ϭ NRRL 2999), was used in this study (36). A. parasiticus NIAH-26 induced all enzymes required to convert norsolorinic acid to aflatoxins in YES liquid culture medium (2% yeast extract, 20% sucrose), although it produced no aflatoxins or anthraquinone or xanthone precursors.…”

Section: Microorganisms and Culturesmentioning

confidence: 99%

“…All known G-group aflatoxin-producing strains also produce B-group aflatoxins (18). No mutants that produce only Ggroup aflatoxins have been isolated in mutagenesis experiments performed with aflatoxigenic strains (3,36). Low levels of conversion of radioactive AFB 1 to other aflatoxins, including AFG 1 , have been obtained by using a cell-free homogenate (22).…”

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confidence: 99%

Enzymatic Formation of G-Group Aflatoxins and Biosynthetic Relationship between G- and B-Group Aflatoxins

Yabe¹,

Nakamura²,

Hamasaki

1999

Appl Environ Microbiol

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We detected biosynthetic activity for aflatoxins G1 and G2 in cell extracts of Aspergillus parasiticusNIAH-26. We found that in the presence of NADPH, aflatoxins G1 and G2 were produced fromO-methylsterigmatocystin and dihydro-O-methylsterigmatocystin, respectively. No G-group aflatoxins were produced from aflatoxin B1, aflatoxin B2, 5-methoxysterigmatocystin, dimethoxysterigmatocystin, or sterigmatin, confirming that B-group aflatoxins are not the precursors of G-group aflatoxins and that G- and B-group aflatoxins are independently produced from the same substrates (O-methylsterigmatocystin and dihydro-O-methylsterigmatocystin). In competition experiments in which the cell-free system was used, formation of aflatoxin G2 from dihydro-O-methylsterigmatocystin was suppressed whenO-methylsterigmatocystin was added to the reaction mixture, whereas aflatoxin G1 was newly formed. This result indicates that the same enzymes can catalyze the formation of aflatoxins G1 and G2. Inhibition of G-group aflatoxin formation by methyrapone, SKF-525A, or imidazole indicated that a cytochrome P-450 monooxygenase may be involved in the formation of G-group aflatoxins. Both the microsome fraction and a cytosol protein with a native mass of 220 kDa were necessary for the formation of G-group aflatoxins. Due to instability of the microsome fraction, G-group aflatoxin formation was less stable than B-group aflatoxin formation. The ordA gene product, which may catalyze the formation of B-group aflatoxins, also may be required for G-group aflatoxin biosynthesis. We concluded that at least three reactions, catalyzed by the ordA gene product, an unstable microsome enzyme, and a 220-kDa cytosol protein, are involved in the enzymatic formation of G-group aflatoxins from eitherO-methylsterigmatocystin or dihydro-O-methylsterigmatocystin.

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Isolation and characterization of Aspergillus parasiticus mutants with impaired aflatoxin production by a novel tip culture method

Cited by 60 publications

References 26 publications

Enzymatic conversion of norsolorinic acid to averufin in aflatoxin biosynthesis

Enzymatic conversion of norsolorinic acid to averufin in aflatoxin biosynthesis

Comparison of the Use of UV Light and Nitrosoguanidine as Mutagenic Treatments in Aspergillus parasiticus

Enzymatic Formation of G-Group Aflatoxins and Biosynthetic Relationship between G- and B-Group Aflatoxins

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