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Ehrlich KC, Chang PK, Scharfenstein LL, Cary JW, Crawford JM, Townsend CA. Absence of the aflatoxin biosynthesis gene, norA, allows accumulation of deoxyaflatoxin B1 in Aspergillus flavus cultures. FEMS Microbiol Lett 2010; 305:65-70. [PMID: 20158523 DOI: 10.1111/j.1574-6968.2010.01914.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Biosynthesis of the highly toxic and carcinogenic aflatoxins in select Aspergillus species from the common intermediate O-methylsterigmatocystin has been postulated to require only the cytochrome P450 monooxygenase, OrdA (AflQ). We now provide evidence that the aryl alcohol dehydrogenase NorA (AflE) encoded by the aflatoxin biosynthetic gene cluster in Aspergillus flavus affects the accumulation of aflatoxins in the final steps of aflatoxin biosynthesis. Mutants with inactive norA produced reduced quantities of aflatoxin B(1) (AFB(1)), but elevated quantities of a new metabolite, deoxyAFB(1). To explain this result, we suggest that, in the absence of NorA, the AFB(1) reduction product, aflatoxicol, is produced and is readily dehydrated to deoxyAFB(1) in the acidic medium, enabling us to observe this otherwise minor toxin produced in wild-type A. flavus.
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Affiliation(s)
- Kenneth C Ehrlich
- Southern Regional Research Center, ARS/USDA, New Orleans, LA 70179, USA.
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Reiss J. Biosynthesewege wichtiger Mykotoxine. J Basic Microbiol 2007. [DOI: 10.1002/jobm.19780181007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Minto RE, Townsend CA. Enzymology and Molecular Biology of Aflatoxin Biosynthesis. Chem Rev 1997; 97:2537-2556. [PMID: 11851470 DOI: 10.1021/cr960032y] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Robert E. Minto
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218
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Watanabe CMH, Townsend CA. Incorporation of Molecular Oxygen in Aflatoxin B1 Biosynthesis. J Org Chem 1996. [DOI: 10.1021/jo952056v] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Coran M. H. Watanabe
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218
| | - Craig A. Townsend
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218
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Luchese RH, Harrigan WF. Biosynthesis of aflatoxin--the role of nutritional factors. THE JOURNAL OF APPLIED BACTERIOLOGY 1993; 74:5-14. [PMID: 8420918 DOI: 10.1111/j.1365-2672.1993.tb02989.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- R H Luchese
- Department of Food Science and Technology, University of Reading, Whiteknights, UK
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Cleveland TE, Bhatnagar D, Brown RL. Aflatoxin production via cross-feeding of pathway intermediates during cofermentation of aflatoxin pathway-blocked Aspergillus parasiticus mutants. Appl Environ Microbiol 1991; 57:2907-11. [PMID: 1746952 PMCID: PMC183895 DOI: 10.1128/aem.57.10.2907-2911.1991] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Cofermentation of Aspergillus parasiticus strains (SRRC 163 and SRRC 2043) blocked at different steps in the aflatoxin B1 (AFB1) biosynthetic pathway in a synthetic liquid medium or on seeds (cottonseed, corn kernels, and peanuts) resulted in production of AFB1. Strain SRRC 2043 accumulated O-methylsterigmatocystin (OMST), a late precursor in AFB1 biosynthesis, whereas SRRC 163 accumulated averantin, an early precursor in the pathway. Strain SRRC 2043 secreted large amounts of OMST in culture relative to the amounts of several other pathway intermediates secreted into media (by other AFB1 pathway-blocked strains). AFB1 production occurred even when colonies of SRRC 163 and SRRC 2043 strains (producing no detectable AFB1) were grown together on an agar medium while physically separated from each other by a filter membrane (0.22-micron pore size). In addition, when mycelia of strain SRRC 163 were added to culture filtrates (containing no mycelia but containing secreted OMST) of strain SRRC 2043, AFB1 production occurred. The results suggested a chemical (rather than genetic) mechanism of complementation for AFB1 production between AFB1 pathway-blocked strains, since no mycelial contact was required between these strains for AFB1 production. The mechanism for chemical complementation involves secretion of OMST by SRRC 2043 and subsequent absorption and conversion of OMST to AFB1 by mycelia of strain SRRC 163.
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Affiliation(s)
- T E Cleveland
- Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana 70124
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Chuturgoon AA, Dutton MF. The affinity purification and characterization of a dehydrogenase from Aspergillus parasiticus involved in aflatoxin B1 biosynthesis. PREPARATIVE BIOCHEMISTRY 1991; 21:125-40. [PMID: 1798691 DOI: 10.1080/10826069108018008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A two step scheme has been developed for the purification of a dehydrogenase from mycelia of 84 hours old Aspergillus parasiticus (1-11-105 Wh 1), which catalyzes the conversion of norsolorinic acid (NA) to averantin (AVN). The dehydrogenase was purified from cell-free extracts using reactive green 19-agarose and norsolorinic acid-agarose affinity chromatography. The latter affinity matrix was synthesised by attaching norsolorinic acid to omega-aminohexylagarose. The purified protein was shown to be homogenous on non-denaturing polyacrylamide gel electrophoresis. A final purification of 215-fold was achieved. Results of gel filtration chromatography indicated the approximate molecular mass of the native protein to be 140,000 daltons. The isoelectric point of the protein was about 5.5 as determined by chromatofocusing. The reaction catalyzed by the dehydrogenase was optimum at pH 8.5 and between 25 degrees to 35 degrees C. The Km of the enzyme for NA and NADPH was determined to be 3.45 microM and 103 microM respectively.
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Affiliation(s)
- A A Chuturgoon
- Department of Biochemistry, University of Natal, Pietermaritzburg, South Africa
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Chuturgoon AA, Dutton MF. The appearance of an enzyme activity catalysing the conversion of norsolorinic acid to averantin in Aspergillus parasiticus cultures. Mycopathologia 1991. [DOI: 10.1007/bf00436386] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Payne GA, Woloshuk CP. Transformation of Aspergillus flavus to study aflatoxin biosynthesis. Mycopathologia 1989; 107:139-44. [PMID: 2515438 DOI: 10.1007/bf00707551] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Aflatoxin contamination of agricultural commodities continues to be a serious problem in the United States. Breeding for resistant genotypes has been unsuccessful and detoxification of food sources is not economically feasible. New strategies for control may become apparent once more is known about the biosynthesis and regulation of aflatoxin. Although the biosynthetic pathway of aflatoxin has been extensively studied, little is known about the regulation of the individual steps in the pathway. We have developed a genetic transformation system for Aspergillus flavus that provides a new and expedient approach to studying the biosynthesis of aflatoxin and its regulation. Through the use of this genetic transformation system, genes for aflatoxin biosynthesis can be identified and isolated by the complementation of aflatoxin negative mutants. In this paper we discuss molecular strategies for studying the regulation and biosynthesis of aflatoxin.
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Affiliation(s)
- G A Payne
- Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616
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Bennett JW, Henderberg A, Grossman K. Sterigmatocystin production on complex and defined substrates. Mycopathologia 1989; 105:35-8. [PMID: 2662007 DOI: 10.1007/bf00443827] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- J W Bennett
- Department of Biology, Tulane University, New Orleans, LA 70118
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Bhatnagar D, Ullah AH, Cleveland TE. Purification and characterization of a methyltransferase from Aspergillus parasiticus SRRC 163 involved in aflatoxin biosynthetic pathway. PREPARATIVE BIOCHEMISTRY 1988; 18:321-49. [PMID: 3237648 DOI: 10.1080/00327488808062532] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A five step scheme has been developed for the purification of a methyltransferase (MT) from mycelia of 3-day old Aspergillus parasiticus (SRRC 163), which catalyzes one step in the aflatoxin biosynthetic pathway. The S-adenosylmethionine (SAM) requiring MT activity is essential for the conversion of sterigmatocystin (ST) to O-methylsterigmatocystin (OMST) prior to being converted to aflatoxin B1. The purification of the MT was carried out from cell-free extracts by CDR (Cell Debris Remover, a cellulosic weak anion exchanger, Whatman) treatment, QMA ACELL, Hydroxylapatite-Ultrogel, PBE 94 chromatofocusing and FractoGel TSK HW-50F filtration chromatography. The purified enzyme was only about 0.1% of the total extractable proteins. The pI of the protein was about 5.0 as judged by chromatofocusing. Results of gel filtration chromatography indicated the approximate molecular mass of the native protein to be 160-KDa. SDS-polyacrylamide gel electrophoresis revealed two protein subunit bands of molecular masses approximately 110-KDa and 58-KDa. The molar extinction coefficient of the enzyme at 280 nm was estimated to be 7.87 X 10(4) M-1 cm-1 in 50 mM potassium phosphate buffer (pH 7.5). The reaction catalyzed by the MT was optimum at pH 7.5 and between 25-35 degrees C. The Km of the enzyme for ST and SAM was determined to be 1.8 microM and 42 microM, respectively with an estimated turnover number of the enzyme for ST of 2.2 X 10(-2) per sec.
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Affiliation(s)
- D Bhatnagar
- Southern Regional Research Laboratory, ARS, USDA, New Orleans, Louisiana 70124
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Yabe K, Ando Y, Hamasaki T. Biosynthetic relationship among aflatoxins B1, B2, G1, and G2. Appl Environ Microbiol 1988; 54:2101-6. [PMID: 3140727 PMCID: PMC202810 DOI: 10.1128/aem.54.8.2101-2106.1988] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Aspergillus parasiticus NIAH-26, a UV-irradiated mutant of A. parasiticus SYS-4 (NRRL 2999), produces neither aflatoxins nor precursors. When sterigmatocystin (ST) or O-methylsterigmatocystin was fed to this mutant in YES medium, aflatoxins B1 (AFB1) and G1 (AFG1) were produced. When dihydrosterigmatocystin (DHST) or dihydro-O-methylsterigmatocystin was fed to this mold, aflatoxins B2 (AFB2) and G2 (AFG2) were produced. The reactions from ST to AFB1 and DHST to AFB2 were also observed in the cell-free system and were catalyzed stepwise by the methyltransferase and oxidoreductase enzymes. In the feeding experiments of strain NIAH-26, the convertibility from ST to AFB1-AFG1 was found to be remarkably suppressed by the coexistence of DHST in the medium, and the convertibility from DHST to AFB2-AFG2 was also suppressed by the presence of ST. When some other mutants which endogenously produce a small amount of aflatoxins (mainly AFB1 and AFG1) were cultured with DHST, the amounts of AFB1 and AFG1 produced were significantly decreased, whereas AFB2 and AFG2 were newly produced. In similar feeding experiments in which 27 kinds of mutants including these mutants were used, most of the mutants which were able to convert exogenous ST to AFB1-AFG1 were also found to convert exogenous DHST to AFB2-AFG2. These results suggest that the same enzymes may be involved in the both biosynthetic pathways from ST to AFB1-AFG1 and DHST to AFB2-AFG2. The reactions described herein were not observed when the molds had been cultured in the YEP medium.
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Affiliation(s)
- K Yabe
- National Institute of Animal Health, Tsukuba-Science City, Ibaraki, Japan
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Mashaly RI, Habib SL, el-Deeb SA, Salem MH, Safwat MM. Isolation, purification and characterization of enzyme(s) responsible for conversion of sterigmatocystin to aflatoxin B1. ZEITSCHRIFT FUR LEBENSMITTEL-UNTERSUCHUNG UND -FORSCHUNG 1988; 186:118-24. [PMID: 3128018 DOI: 10.1007/bf01042704] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The cell-free extract prepared from Aspergillus flavus ATCC 5517/A 228 showed activity in converting sterigmatocystin to aflatoxin B1. The extract was purified on Ultrogel AcA-54 and resulted in ten protein peaks, one of which (peak VI) showed activity in sterigmatocystin conversion. The protein in this peak gave one protein band using polyacrylamide gel (PAG)-disc electrophoresis. For further purification, protein(s) in peak VI were applied on DEAE-Sephadex A-50 and two protein peaks were detected. Only one peak showed enzyme activity which showed homogeneity as one band on PAGE and sodium dodecyl sulphate (SDS)-PAGE. The optimum temperature for the enzyme activity was 28 degrees C and the optimum pH was 8. The maximum conversion resulted from the action of 0.6 mg enzyme protein on 48 X 10(-8) mol sterigmatocystin. Zn2+, Co2+ and Mn2+ enhanced the enzyme activity, while ethylenediaminetetraacetic acid, parahydroxymercuric benzoate and phenylmethylsulphonic fluoride inhibited the enzyme activity in a dose-dependent manner. Amino-acid analysis showed the presence of 22 amino acids, three of which are unknown. The enzyme has a molecular weight of 64,000 daltons (by gel filtration) and 70,000 daltons (by SDS-PAGE).
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Affiliation(s)
- R I Mashaly
- Biotechnology Laboratory, University of Alexandria Research Center UNARC, Egypt
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The involvement of cytochromeP-450 monooxygenase system in aflatoxin biosynthesis byAspergillus flavus. ACTA ACUST UNITED AC 1987. [DOI: 10.1007/bf01569420] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Cleveland TE, Lax AR, Lee LS, Bhatnagar D. Appearance of enzyme activities catalyzing conversion of sterigmatocystin to aflatoxin B1 in late-growth-phase Aspergillus parasiticus cultures. Appl Environ Microbiol 1987; 53:1711-3. [PMID: 3116930 PMCID: PMC203939 DOI: 10.1128/aem.53.7.1711-1713.1987] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Two activities involved in terminal pathway conversion of sterigmatocystin to aflatoxin B1 were isolated from an aflatoxin-nonproducing mutant of Aspergillus parasiticus (avn-1), and the time course of appearance of the activities in culture was determined. Subcellular fractionation of fungal mycelia resolved the two activities into a postmicrosomal activity which catalyzed conversion of sterigmatocystin to O-methylsterigmatocystin and a microsomal activity which converted O-methylsterigmatocystin to aflatoxin B1. The two activities were absent in 24-h-old cells, increased to optimum levels during the stationary phase, and then declined.
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Affiliation(s)
- T E Cleveland
- Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana 70179
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Bhatnagar D, McCormick SP, Lee LS, Hill RA. Identification of O-methylsterigmatocystin as an aflatoxin B1 and G1 precursor in Aspergillus parasiticus. Appl Environ Microbiol 1987; 53:1028-33. [PMID: 3111363 PMCID: PMC203804 DOI: 10.1128/aem.53.5.1028-1033.1987] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
An isolate of Aspergillus parasiticus CP461 (SRRC 2043) produced no detectable aflatoxins, but accumulated O-methylsterigmatocystin (OMST). When sterigmatocystin (ST) was fed to this isolate in a low-sugar medium, there was an increase in the accumulation of OMST, without aflatoxin synthesis. When radiolabeled [14C]OMST was fed to resting mycelia of a non-aflatoxin-, non-ST-, and non-OMST-producing mutant of A. parasiticus AVN-1 (SRRC 163), 14C-labeled aflatoxins B1 and G1 were produced; 10 nmol of OMST produced 7.8 nmol of B1 and 1.0 nmol of G1, while 10 nmol of ST produced 6.4 nmol of B1 and 0.6 nmol of G1. A time course study of aflatoxin synthesis in ST feeding experiments with AVN-1 revealed that OMST is synthesized by the mold during the onset of aflatoxin synthesis. The total amount of aflatoxins recovered from OMST feeding experiments was higher than from experiments in which ST was fed to the resting mycelia. These results suggest that OMST is a true metabolite in the aflatoxin biosynthetic pathway between sterigmatocystin and aflatoxins B1 and G1 and is not a shunt metabolite, as thought previously.
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Bhatnagar RK, Ahmad S, Mukerji KG, Subramanian TA. Pyridine nucleotides and redox state regulation of aflatoxin biosynthesis in Aspergillus parasiticus NRRL 3240. THE JOURNAL OF APPLIED BACTERIOLOGY 1986; 60:135-41. [PMID: 3700278 DOI: 10.1111/j.1365-2672.1986.tb03370.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In vivo regulation of lipid and aflatoxin biosynthesis by pyridine nucleotides and their derived functions was studied in Aspergillus parasiticus NRRL 3240. Aflatoxins, total lipids and pyridine nucleotide content were estimated under different growth conditions. Aflatoxin formation was highest in cultures grown in sucrose-low salts medium followed by asparagine- and zinc-deficient media. The lipid content of the cultures followed an inverse pattern. The levels of oxidized nucleotides decreased with age under all culture conditions employed. Concentrations of NADPH peaked before the onset of aflatoxin biosynthesis. For each medium used, the estimated catabolite reduction charge was constant at all stages of growth whereas the anabolic reduction charge varied. A direct relationship between the level of extracellular ammonium ions and anabolic reduction charge was established. A high anabolic reduction charge was associated with increased lipid biosynthesis rather than aflatoxin biosynthesis.
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Buchanan RL, Lewis DF. Regulation of aflatoxin biosynthesis: effect of glucose on activities of various glycolytic enzymes. Appl Environ Microbiol 1984; 48:306-10. [PMID: 6091545 PMCID: PMC241508 DOI: 10.1128/aem.48.2.306-310.1984] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Catabolism of carbohydrates has been implicated in the regulation of aflatoxin synthesis. To characterize this effect further, the activities of various enzymes associated with glucose catabolism were determined in Aspergillus parasiticus organisms that were initially cultured in peptone-mineral salts medium and then transferred to glucose-mineral salts and peptone-mineral salts media. After an initial increase in activity, the levels of glucose 6-phosphate dehydrogenase, mannitol dehydrogenase, and malate dehydrogenase were lowered in the presence of glucose. Phosphofructokinase activity was greater in the peptone-grown mycelium, but fructose diphosphatase was largely unaffected by carbon source. Likewise, carbon source had relatively little effect on the activities of pyruvate kinase, malic enzyme, isocitrate-NADP dehydrogenase, and isocitrate-NAD dehydrogenase. The results suggest that glucose may, in part, regulate aflatoxin synthesis via a carbon catabolite repression of NADPH-generating and tricarboxylic acid cycle enzymes.
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Jeenah MS, Dutton MF. The conversion of sterigmatocystin to O-methylsterigmatocystin and aflatoxin B1 by a cell-free preparation. Biochem Biophys Res Commun 1983; 116:1114-8. [PMID: 6418171 DOI: 10.1016/s0006-291x(83)80257-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A cell-free system derived from a versicolorin A-accumulating mutant of Aspergillus parasiticus was found to convert sterigmatocystin to both O-methylsterigmatocystin and aflatoxin B1. It is suggested that the similarity in the chromatographic properties of these two metabolites has caused erroneous conclusions to be made with regards to the biosynthesis of aflatoxin B1.
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Yousef AE, Marth EH. Incorporation of [14C]acetate into aflatoxin by resting cultures of Aspergillus parasiticus in the presence of antifungal agents. ACTA ACUST UNITED AC 1983. [DOI: 10.1007/bf00500832] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Bennett JW, Christensen SB. New perspectives on aflatoxin biosynthesis. ADVANCES IN APPLIED MICROBIOLOGY 1983; 29:53-92. [PMID: 6650265 DOI: 10.1016/s0065-2164(08)70354-x] [Citation(s) in RCA: 111] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Dutton MF, Anderson MS. Role of versicolorin A and its derivatives in aflatoxin biosynthesis. Appl Environ Microbiol 1982; 43:548-51. [PMID: 6803669 PMCID: PMC241872 DOI: 10.1128/aem.43.3.548-551.1982] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The involvement of various anthraquinone metabolites in the biosynthesis of aflatoxin B1 was investigated by using a labeled double-substrate technique in a cell-free system. The results showed that both versicolorin A hemiacetal and versicolorin A hemiacetal acetate were converted to aflatoxin B1, whereas versicolorin A was not, even though it was added to the same cell-free system. Thus, versicolorin A hemiacetal, versicolorin A hemiacetal acetate, or both were implicated as key intermediates, whereas versicolorin A and C became side shunt metabolites. These latter compounds reentered the pathway depending on the availability of the appropriate enzymes and suitability of conditions. Dichlorvos, a specific inhibitor of aflatoxin biosynthesis, is considered to have its primary action on either an oxygenase or dehydrogenase involved in the pathway and to act in a secondary capacity as an inhibitor of an esterase which may also be involved in the pathway.
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Abstract
Aflatoxin B2 is a secondary metabolite produced by the ubiquitous molds Aspergillus flavus and Aspergillus parasiticus. The toxin was first characterized in 1963 as the etiological agent responsible for the infamous "Turkey X' disease. Since that time, much information on its chemistry, toxicity and biological activity has accumulated. A significant amount of work has been done to elucidate its biosynthesis. Evidence indicates the polyketide route as its point of origin. The steps involved in the polyketide pathway, the six identified intermediated compounds, and the experimental techniques and analytical instrumentation used to procure information on aflatoxin biogenesis are included in this review.
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Zamir LO, Hufford KD. Precursor recognition by kinetic pulse-labeling in a toxigenic aflatoxin B1-producing strain of Aspergillus. Appl Environ Microbiol 1981; 42:168-73. [PMID: 6789767 PMCID: PMC243979 DOI: 10.1128/aem.42.1.168-173.1981] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Kinetic pulse-labeling of aflatoxin pathway compounds was carried out in Aspergillus parasiticus, beginning with radioactive acetate. Norsolorinic acid, averufin, versicolorin A, and sterigmatocystin (all known as compounds which can be incorporated into the aflatoxin molecule) were radiotraced to follow their order of appearance. Aflatoxin species B1, B2, G1, and G2 were included. Norsolorinic acid and averufin appeared as early transient intermediates followed in order by versicolorin A, aflatoxins, and sterigmatocystin. To date, a mutually confirming array of results has been obtained with established precursors in wild-type strains of A. parasiticus and A. versicolor (as well as with an aflatoxin pathway mutant of A. parasiticus), which together establish a practical methodology for recognition of new pathway intermediates. The kinetic of pulse-labeling for sterigmatocystin in relation to aflatoxins suggests that duel branchlets may exist to flatoxins; i.e., sterigmatocystin may not be an obligatory aflatoxin precursor.
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Tyagi JS, Tyagi AK, Venkitasubramanian TA. Some factors regulating [1-14C] acetate incorporation into aflatoxins by spheroplasts and spheroplast lysates from Aspergillus. Toxicon 1981; 19:445-54. [PMID: 6800068 DOI: 10.1016/0041-0101(81)90002-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Grootwassink JW, Gaucher GM. De novo biosynthesis of secondary metabolism enzymes in homogeneous cultures of Penicillium urticae. J Bacteriol 1980; 141:443-55. [PMID: 6988382 PMCID: PMC293646 DOI: 10.1128/jb.141.2.443-455.1980] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The initiation of patulin biosynthesis in submerged batch cultures of Penicillium urticae NRRL 2159A was investigated at the enzyme level. In contrast to earlier studies, this study achieved a clear temporal separation of growing cells devoid of secondary metabolism-specific enzymes from nongrowing cells, which rapidly produce these enzymes. A spore inoculum, silicone-treated flasks, and two new media which supported a rapid, pellet-free, filamentous type of growth were used. In yeast extract-glucose-buffer medium, a marked drop in the specific growth rate (approximately equal to 0.26 h-1) coincided with the appearance of the first pathway-specific enzyme, 6-methylsalicylic acid synthetase, at about 19 h after inoculation. About 3 h later, when replicatory growth had ceased entirely, the sparsely branched mycelia (length, approximately equal to 550 microns) began the rapid synthesis of a later pathway enzyme, m-hydroxybenzyl alcohol dehydrogenase. A similar sequence of events occurred in a defined nitrate-glucose-buffer medium; 12 other strains or isolates of P. urticae, as well as some patulin-producing aspergilli, behaved in a similar manner. The age at which a culture produced m-hydroxybenzyl alcohol dehydrogenase was increased by increasing the nutrient nitrogen content of the medium or by decreasing the size of the spore inoculum. In each instance the appearance of enzyme was determined by the nutritional status of the culture and not by its age. A similar appearance of patulin pathway enzymes occurred when a growing culture was resuspended in a nitrogen-free 4% glucose solution with or without 0.1 M phosphate (pH 6.5). The appearance of both the synthetase and the dehydrogenase was arrested by the addition of cycloheximide (0.4 to 5 micrograms/ml) or actinomycin D (20 to 80 micrograms/ml). This requirement for de novo protein and ribonucleic acid syntheses was confirmed by the incorporation of labeled leucine into the dehydrogenase, and the possibility that latent or preformed proteins were being activated was eliminated.
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Rao VM, Maggon KK, Venkitasubramanian TA. Oxidases in Aspergillus parasiticus in relation to aflatoxin biosynthesis. Toxicon 1980; 18:279-83. [PMID: 7394817 DOI: 10.1016/0041-0101(80)90006-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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32
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Zum wahrscheinlichen Vorkommen von Sterigmatocystin in Milch und dessen Verhalten in K�se. Eur Food Res Technol 1980. [DOI: 10.1007/bf01045872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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33
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Lafont P, Debeaupuis JP. [Effect of sterigmatocystin on the toxinogenesis of the Aspergillus flavus group]. Mycopathologia 1979; 69:187-92. [PMID: 119164 DOI: 10.1007/bf00452833] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The aflatoxinogenesis of Aspergillus parasiticus is significantly enhanced by the presence, in the medium, of sterigmatocystin at a high level (35--50 microgram/ml); low concentrations, in the order of 175 microgram/ml, have no effect on the production of aflatoxins. During the period where the aflatoxinogenesis of the culture is high, no variation of the sterigmatocystin level is noted, Experiments with 14C-sterigmatocystin indicate that the mold does not utilize the metabolite itself as a precursor of aflatoxins.
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Anderson MS, Dutton MF. The use of cell free extracts derived from fungal protoplasts in the study of aflatoxin biosynthesis. EXPERIENTIA 1979; 35:21-2. [PMID: 105924 DOI: 10.1007/bf01917850] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A supernatant fraction derived from protoplasts of Aspergillus flavus was shown to be capable of converting both sterigmatocystin and versiconal hemiacetal acetate to aflatoxin B1. Versicolorin A was not converted under the same conditions.
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Dutton MF, Anderson MS. The use of fungal protoplasts in the study of aflatoxin biosynthesis. EXPERIENTIA 1978; 34:22-4. [PMID: 413736 DOI: 10.1007/bf01921878] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Protoplasts derived from Aspergillus flavus are shown to be capable of synthesizing aflatoxins when incubated in a chemically defined medium. 14C-Acetate and 14C-Versicolorin A, added to protoplasts from 3-day-old mycelium, are incorporated into aflatoxin B1.
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Reiss J. [Biosynthetic pathways of important mycotoxins]. ZEITSCHRIFT FUR ALLGEMEINE MIKROBIOLOGIE 1978; 18:747-57. [PMID: 111430 DOI: 10.1002/jobm.3630181007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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37
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Microbial Transformations of Antibiotics. ACTA ACUST UNITED AC 1978. [DOI: 10.1016/b978-0-12-040302-8.50015-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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38
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Maggon KK, Gupta SK, Venkitasubramanian TA. Biosynthesis of aflatoxins. BACTERIOLOGICAL REVIEWS 1977; 41:822-55. [PMID: 23090 PMCID: PMC414029 DOI: 10.1128/br.41.4.822-855.1977] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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39
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Rabie CJ, Steyn M, van Schalkwyk GC. New species of Aspergillus producing sterigmatocystin. Appl Environ Microbiol 1977; 33:1023-5. [PMID: 406838 PMCID: PMC170821 DOI: 10.1128/aem.33.5.1023-1025.1977] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
A number of species belonging to the genus Aspergillus were evaluated for their toxicity to ducklings and the ability to produce sterigmatocystin. Three new species capable of producing sterigmatocystin were found, namely, Aspergillus aurantio-brunneus, Aspergillus quadrilineatus, and Aspergillus ustus. All three were toxic to ducklings. The production of sterigmatocystin by Aspergillus rugulosus was confirmed, and the toxicity of Aspergillus stellatus and Aspergillus multicolor is described.
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Singh R, Hsieh DP. Aflatoxin biosynthetic pathway: elucidation by using blocked mutants of Aspergillus parasiticus. Arch Biochem Biophys 1977; 178:285-92. [PMID: 836036 DOI: 10.1016/0003-9861(77)90193-x] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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