Individual reaction requirements of two enzyme activities, isolated from Aspergillus parasiticus, which together catalyze conversion of sterigmatocystin to aflatoxin B1

1987 ◽  
Vol 33 (12) ◽  
pp. 1108-1112 ◽  
Author(s):  
Thomas E. Cleveland ◽  
Deepak Bhatnagar
Keyword(s):  
Aflatoxin B1 ◽  
Enzyme Activities ◽  
Microsomal Fraction ◽  
Aspergillus Parasiticus ◽  
Heat Treated ◽  
Individual Reaction ◽  
Aflatoxin B

Individual reaction requirements were determined for each of two enzyme activities present in Aspergillus parasiticus mycelia which together catalyze conversion of sterigmatocystin (ST) to aflatoxin B1 (AFB1). A postmicrosomal activity (PMA) catalyzed conversion of ST to O-methylsterigmatocystin (OMST) and a microsomal activity (MA) catalyzed conversion of OMST to AFB1. PMA was stimulated two- to three-fold in the presence of S-adenosylmethionine. Addition of NADPH promoted the maximum MA; this activity was not detected when FAD, FMN, NAD, or NADH were utilized individually as cofactors in reaction mixtures. A substantial amount (62%) of MA was lost during isolation of the microsomal fraction, but the activity was completely restored by reconstitution with a heat-treated (100 °C) postmicrosomal fraction. The reaction catalyzed by MA was optimum at pH 7.0 and at 17–23 °C, whereas the PMA reaction was optimum at pH 8.0–8.5 and at 35–40 °C. Apparent Km values of approximately 2.6 × 10−6 M (for ST) and 6.6 × 10−7 M (for OMST) were determined for PMA and MA, respectively.

Secondary biosynthesis of aflatoxin B1 in Aspergillus parasiticus

1970 ◽  
Vol 16 (10) ◽  
pp. 959-963 ◽  
Author(s):  
R. W. Detroy ◽  
C. W. Hesseltine
Keyword(s):  
Protein Synthesis ◽  
Aflatoxin B1 ◽  
Aspergillus Parasiticus ◽  
Synthetase Activity ◽  
Macromolecular Synthesis ◽  
High Concentration ◽  
Methyl Group ◽  
Aflatoxin B ◽  
Concentration Levels

The effect of two inhibitors on the formation of aflatoxin B1 synthetase activity in strain NRRL 2999 Aspergillus parasiticus has been studied. Aflatoxin B1 synthesizing activity was measured in vivo by incorporation of the 14C-methionine methyl group into aflatoxin B1. Cycloheximide at a concentration of 150 μg/ml blocks protein synthesis completely. If addition of cycloheximide is made before B1 synthetase appears, no activity accumulates; if added during accumulation, activity is frozen at the level reached at the time of addition. The cycloheximide effect is reversible since morphogenesis, total protein synthesis, and aflatoxin B1 synthetase activity all resume after removal of the inhibitor.DL-p-Fluorophenylalanine partially inhibits aflatoxin B1 synthesis in vivo; however, its effect upon macromolecular synthesis is incomplete even at high concentration levels. Once formed, the aflatoxin synthetase appears to maintain B1 synthesis when further protein synthesis is blocked; i.e., it is not rapidly degraded.

Aflatoxin B1 Cytotoxicity in Neurons in Culture

1996 ◽  
Vol 24 (4) ◽  
pp. 533-540 ◽  
Author(s):  
Paola Bonsi ◽  
Maura Palmery ◽  
Gabriella Augusti-Tocco
Keyword(s):  
Motor Neurons ◽  
Aspergillus Parasiticus ◽  
Neuronal Cell ◽  
Cell Number ◽  
Human Brain Tissue ◽  
Proliferating Cells ◽  
Toxin Concentration ◽  
Lower Extent ◽  
Neuronal Cell Lines ◽  
Aflatoxin B

Aflatoxin B1 (AFB1), a metabolite produced by Aspergillus flavus and Aspergillus parasiticus, is mainly known for its strong hepatotoxic and hepatocarcinogenic actions. Acute and reversible effects due to exposure to aflatoxin and the presence of aflatoxins in various human tissues and organs have also been reported. In particular, aflatoxin M1 (a metabolite of AFB1) has been identified in human brain tissue, and a syndrome characterised by encephalopathy has been observed in humans poisoned by AFB1. As a first approach to the study of the neurotoxicity of AFB1, we used the human neuronal cell lines, SKNMC and SKNSH. The data reported show clearly that AFB1 is capable of interacting directly with neuronal cells and causing a decrease in cell number following the addition of toxin to the culture. Decrease in cell survival is dependent on the toxin concentration, on time of exposure, and on cell density. The cytotoxic response of these cells has been compared to the effects of AFB1 on hepatoma cells and spinal cord motor neurons. Postmitotic neurons are also susceptible to AFB1 toxicity, although to a lower extent than proliferating cells. A non-proliferating state thus appears to lower, but not destroy, neuron sensitivity to the toxin.

Confirmatory Tests for Aflatoxin B1

1964 ◽  
Vol 47 (5) ◽  
pp. 801-803 ◽  
Author(s):  
Peter John Andrellos ◽  
George R Reid
Keyword(s):  
Acetic Acid ◽  
Thin Layer ◽  
Formic Acid ◽  
Thionyl Chloride ◽  
Aflatoxin B1 ◽  
Trifluoroacetic Acid ◽  
Reaction Products ◽  
Confirmatory Tests ◽  
Aflatoxin B ◽  
Layer Chromatography

Abstract Three confirmatory tests have been devised to identify aflatoxin B±. Portions of the isolated toxin are treated with formic acid-thionyl chloride, acetic acid-thionyl chloride, and trifluoroacetic acid, respectively, and aliquots of the three fluorescent reaction products are spotted on thin-layer chromatography plates. Standards treated with each of the three reagents, plus an untreated standard, are spotted on the same plate, and after development the spots are compared under ultraviolet light.

scholarly journals Production of aflatoxins and aflatoxicols by Aspergillus flavus and Aspergillus parasiticus and metabolism of aflatoxin B1 by aflatoxin-non-producing Aspergillus flavus.

Eisei kagaku ◽  
1991 ◽  
Vol 37 (2) ◽  
pp. 107-116 ◽  
Author(s):  
MITSUO NAKAZATO ◽  
SATOSHI MOROZUMI ◽  
KAZUO SAITO ◽  
KENJI FUJINUMA ◽  
TAICHIRO NISHIMA ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Aspergillus Parasiticus

scholarly journals Enzymatic activity in turkey, duck, quail and chicken liver microsomes against four human cytochrome P450 prototype substrates and aflatoxin B1

2011 ◽  
Vol 1 (1) ◽  
pp. 4 ◽  
Author(s):  
Hansen W. Murcia ◽  
Gonzalo J. Díaz ◽  
Sandra Milena Cepeda
Keyword(s):  
Cytochrome P450 ◽  
Aflatoxin B1 ◽  
Enzyme Activities ◽  
High Performance ◽  
Biochemical Characterization ◽  
Liver Microsomes ◽  
Cytochrome P450 Enzymes ◽  
Catalytic Rate

Cytochrome P450 enzymes (CYP) are a group of monooxygenases able to biotransform several kinds of xenobiotics including aflatoxin B1 (AFB1), a highly toxic mycotoxin. These enzymes have been widely studied in humans and others mammals, but there is not enough information in commercial poultry species about their biochemical characteristics or substrate specificity. The aim of the present study was to identify CYPs from avian liver microsomes with the use of prototype substrates specific for human CYP enzymes and AFB1. Biochemical characterization was carried out in vitro and biotransformation products were detected by high-performance liquid chromatography (HPLC). Enzymatic constants were calculated and comparisons between turkey, duck, quail and chicken activities were done. The results demonstrate the presence of four avian ortholog enzyme activities possibly related with a CYP1A1, CYP1A2, CYP2A6 (activity not previously identified) and CYP3A4 poultry orthologs, respectively. Large differences in enzyme kinetics specific for prototype substrates were found among the poultry species studied. Turkey liver microsomes had the highest affinity and catalytic rate for AFB1 whereas chicken enzymes had the lowest affinity and catalytic rate for the same substrate. Quail and duck microsomes showed intermediate values. These results correlate well with the known in vivo sensitivity for AFB1 except for the duck. A high correlation coefficient between 7-ethoxyresorufin-Odeethylase (EROD) and 7-methoxyresorufin- O-deethylase (MROD) activities was found in the four poultry species, suggesting that these two enzymatic activities might be carried out by the same enzyme. The results of the present study indicate that four prototype enzyme activities are present in poultry liver microsomes, possibly related with the presence of three CYP avian orthologs. More studies are needed in order to further characterize these enzymes.

Effects of Potassium Sorbate on Growth and Aflatoxin Production by Aspergillus parasiticus and Aspergillus flavus1

1983 ◽  
Vol 46 (11) ◽  
pp. 940-942 ◽  
Author(s):  
LLOYD B. BULLERMAN
Keyword(s):  
Aspergillus Flavus ◽  
Yeast Extract ◽  
Aflatoxin B1 ◽  
Spore Germination ◽  
Mycelial Growth ◽  
Aspergillus Parasiticus ◽  
Aflatoxin Production ◽  
Potassium Sorbate ◽  
Mycelial Mass ◽  
Yeast Extract Sucrose

Growth and aflatoxin production by selected strains of Aspergillus parasiticus and Aspergillus flavus in the presence of potassium sorbate at 12°C were studied. Potassium sorbate at 0.05, 0.10 and 0.15% delayed or prevented spore germination and initiation of growth, and slowed growth of these organisms in yeast-extract sucrose broth at 12°C. Increasing concentrations of sorbate caused more variation in the amount of total mycelial growth and generally resulted in a decrease in total mycelial mass. Potassium sorbate also greatly reduced or prevented production of aflatoxin B1 by A. parasiticus and A. flavus for up to 70 d at 12°C. At 0.10 and 0.15% of sorbate, aflatoxin production was essentially eliminated. A 0.05% sorbate, aflatoxin production was greatly decreased in A. flavus over the control, but only slightly decreased in A. parasiticus.

Preparation of 14C-Labeled Aflatoxin B1

1973 ◽  
Vol 56 (3) ◽  
pp. 643-646
Author(s):  
Grant L Schoenhard ◽  
Russell O Sinnhuber ◽  
Donald J Lee
Keyword(s):  
Trace Metals ◽  
Primary Culture ◽  
Silica Gel ◽  
Aflatoxin B1 ◽  
Aspergillus Parasiticus ◽  
Specific Activity ◽  
Ultraviolet Spectrum ◽  
Reference Standard ◽  
Chemical Purity ◽  
Chloroform Methanol

Abstract A successful method to obtain 14C-labeled aflatoxin B1 from Aspergillus parasiticus ATCC 15517 was developed. The nitrogen-free resting culture contained mycelia from a 72 hr primary culture, 0.02M glucose, 0.005M (1 mCi/mmole) acetate-1-14C, salts, and trace metals. It was incubated 12 hr at 30°C. Aflatoxin B1-14C was isolated from chloroform extracts of the resting culture by column chromatography on silica gel H eluted under pressure with a continuous gradient of chloroform to chloroform-methanol (98+2). The ultraviolet spectrum of the 14C-labeled aflatoxin was examined. The ratios of the absorbances at 220/265 and 362/265 nm compared to established values and a reference standard were used as criteria of chemical purity. Label integrity was verified by chromatography, hydrogenation to the tetrahydrodeoxoaflatoxin B1, and conversion to the hemiacetal and the epimeric acetates. After purification, 1.37 mg 14C-labeled aflatoxin B1 of specific activity 744 μCi/mmole was obtained from 2 mCi acetate-1-14C of specific activity 1 mCi/mmole.

scholarly journals Urinary excretion of aflatoxin M1 after administration of aflatoxin B1 in sucrose- or starch-rich diets

1978 ◽  
Vol 40 (2) ◽  
pp. 397-401 ◽  
Author(s):  
A. Wise ◽  
M. Suzangar ◽  
M. Messripour ◽  
J. Mohammadi
Keyword(s):  
Urinary Excretion ◽  
Aflatoxin B1 ◽  
Aflatoxin M1 ◽  
Sprague Dawley ◽  
Drug Metabolizing Enzyme ◽  
Sprague Dawley Rats ◽  
Metabolizing Enzyme ◽  
Aflatoxin B

1. Male Sprague–Dawley rats were given 630 g/kg sucrose or starch with 2 mg/kg aflatoxin B1 for periods of 75, 145 and 200 d, and the 24 h urinary excretion of aflatoxin M1 was measured.2. Less aflatoxin M1 was excreted by the rats fed on the sucrose-rich diet compared to those fed on the starch-rich diet. This difference was especially marked when expressed per g metabolizing tissue.3. It is concluded that sucrose probably decreases the activity of aflatoxin B1 metabolism in a similar way to its previously found effect on the drug-metabolizing enzyme.

Effect of Storage Treatments on Anthocyanin, Fumonisin B1, Aflatoxin B1 Content of Anthocyanin Extract from Purple Corn (Zea may L.) in North China

2011 ◽  
Vol 361-363 ◽  
pp. 759-763
Author(s):  
Chao Zhang ◽  
Yue Ma ◽  
Xiao Yan Zhao ◽  
Fen Wang
Keyword(s):  
Aflatoxin B1 ◽  
North China ◽  
Fumonisin B1 ◽  
Anthocyanin Content ◽  
Zea May ◽  
Purple Corn ◽  
Aflatoxin B ◽  
Anthocyanin Production

Effects of storage treatments on anthocyanin, fumonisin B1, aflatoxin B1 content of anthocyanin extract from purple corn were evaluated based on the harvest of 2008 and 2009 in north China. The anthocyanin content of anthocyanin extract from husk was 62.4 g/kg, being significant higher than that from cob and seed. The fumonisin B1 and aflatoxin B1 content of anthocyanin extract from the husk were 4.25 and 5.60 μg/kg, respectively, according with legislative limitation of USFDA. Moreover, the fumonisin B1 and aflatoxin B1 content of anthocyanin extract from the husk were lower than the maximum limitation of USFDA after each storage treatments. Therefore, the husk of the purple corn in north China was feasible for anthocyanin production due to its high anthocyanin content and low fumonisin B1 and aflatoxin B1 content.

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