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.

scholarly journals Effects of the hepatotoxic agents retrorsine and aflatoxin B1 on hepatic protein synthesis in the rat

1968 ◽  
Vol 109 (1) ◽  
pp. 87-91 ◽  
Author(s):  
S. Villa-Treviño ◽  
D. D. Leaver
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Rat Liver ◽  
Aflatoxin B1 ◽  
Plasma Proteins ◽  
Pyrrolizidine Alkaloid ◽  
Main Site ◽  
Nuclear Rna ◽  
Hepatic Protein Synthesis

1. Aflatoxin and the pyrrolizidine alkaloid retrorsine inhibited the incorporation of labelled amino acids into rat liver and plasma proteins in vivo. Inhibition was greater and detected earlier with retrorsine (1hr.) than with aflatoxin (3hr.). 2. Both toxins affected the liver ribosomal aggregates, causing increases in the proportion of monomers plus dimers. The effect of retrorsine was greater than that of aflatoxin. 3. Incorporation of labelled amino acids into proteins of cell-free preparations of liver from rats treated with aflatoxin was lower than in control preparations. The main site of inhibition appeared to be the ribosomes. 4. Both toxins inhibited the incorporation of orotate into liver nuclear RNA 1hr. after administration.

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.

scholarly journals In vivo effect of aflatoxin B1 , on protein synthesis in rat liver

FEBS Letters ◽  
1973 ◽  
Vol 29 (3) ◽  
pp. 329-332 ◽  
Author(s):  
A. Sarasin ◽  
Y. Moulé ◽  
N. Darracq
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Aflatoxin B1

scholarly journals In Vivo Crystallization of Human IgG in the Endoplasmic Reticulum of Engineered Chinese Hamster Ovary (CHO) Cells

2011 ◽  
Vol 286 (22) ◽  
pp. 19917-19931 ◽  
Author(s):  
Haruki Hasegawa ◽  
John Wendling ◽  
Feng He ◽  
Egor Trilisky ◽  
Riki Stevenson ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Cho Cells ◽  
Membrane Integrity ◽  
Chinese Hamster ◽  
High Concentration ◽  
Human Igg ◽  
Secretory Capacity

Protein synthesis and secretion are essential to cellular life. Although secretory activities may vary in different cell types, what determines the maximum secretory capacity is inherently difficult to study. Increasing protein synthesis until reaching the limit of secretory capacity is one strategy to address this key issue. Under highly optimized growth conditions, recombinant CHO cells engineered to produce a model human IgG clone started housing rod-shaped crystals in the endoplasmic reticulum (ER) lumen. The intra-ER crystal growth was accompanied by cell enlargement and multinucleation and continued until crystals outgrew cell size to breach membrane integrity. The intra-ER crystals were composed of correctly folded, endoglycosidase H-sensitive IgG. Crystallizing propensity was due to the intrinsic physicochemical properties of the model IgG, and the crystallization was reproduced in vitro by exposing a high concentration of IgG to a near neutral pH. The striking cellular phenotype implicated the efficiency of IgG protein synthesis and oxidative folding exceeded the capacity of ER export machinery. As a result, export-ready IgG accumulated progressively in the ER lumen until a threshold concentration was reached to nucleate crystals. Using an in vivo system that reports accumulation of correctly folded IgG, we showed that the ER-to-Golgi transport steps became rate-limiting in cells with high secretory activity.

Protein synthesis in a fish heart: responses to increased power output

1988 ◽  
Vol 137 (1) ◽  
pp. 565-587 ◽  
Author(s):  
D. F. Houlihan ◽  
C. Agnisola ◽  
A. R. Lyndon ◽  
C. Gray ◽  
N. M. Hamilton
Keyword(s):  
Protein Synthesis ◽  
Cardiac Output ◽  
Oxygen Consumption ◽  
Power Output ◽  
Coronary Vessels ◽  
High Concentration ◽  
Fish Heart ◽  
Bulbus Arteriosus

The effects of exercise on the rates of protein synthesis in the chambers of the trout heart were investigated in vitro and in vivo. An in vitro rainbow trout heart preparation was developed which permitted perfusion of the coronary supply to the compact region of the ventricular muscle. This preparation was used to examine the mechanical responses to preload pressures, the oxygen consumption at different power outputs and the rates of protein synthesis in the various heart components. By increasing preload pressure it was possible to double cardiac output, oxygen consumption and power output without changing heart rate. Mechanical efficiency of the hearts was approximately 20%. Perfusion of the coronary vessels improved cardiac output. Protein synthesis was measured in isolated hearts by the incorporation of [3H]phenylalanine added at high concentration (1.35 mmol l-1) to the perfusion medium. The various chambers of the heart showed marked differences in their rates of protein synthesis. Increasing cardiac output and power output in vitro by twofold over 20 min increased the fractional rate of protein synthesis by approximately 2.5-fold in the atrium and ventricle but did not affect the rates in the bulbus arteriosus. Perfusion of the coronary vessels significantly increased the rates of protein synthesis of the compact layer of the ventricle. In vivo there were no significant differences in the fractional protein synthesis rates between the atrium and ventricle; slow-speed continuous swimming over 40 min (1.5 body lengths s-1) caused an increase in the rates of protein synthesis in all the chambers except the bulbus arteriosus. The stimulation in the fractional rates of protein synthesis by approximately 32% was not as great as in vitro. Both in vivo and in vitro the increased rates of protein synthesis occurred without any change in RNA to protein ratios, indicating an improved activity of protein synthesis per unit of RNA. It is concluded that short-term increases in cardiac contractility, possibly acting through the mechanical stretch on the cardiac muscle, stimulated protein synthesis, particularly in the ventricle, through increased ribosomal activity.

An Evaluation of the Metabolic Basis of Aflatoxin B1 Toxicity by Using Buffalo Granulocytes and Agranulocytes In Vitro

2005 ◽  
Vol 33 (4) ◽  
pp. 387-390 ◽  
Author(s):  
Tukaram More ◽  
Golla Ramalinga Reddy ◽  
Sandeep Kumar
Keyword(s):  
Protein Synthesis ◽  
Atpase Activity ◽  
Aflatoxin B1 ◽  
Cell Types ◽  
Leucine Incorporation ◽  
Transferase Activity ◽  
Metabolic Basis ◽  
Aflatoxin B ◽  
In Cells

This study was aimed at monitoring cytotoxic changes in buffalo leukocyte subpopulations exposed to aflatoxin B1 (AFB1), since no such information is available for this species. The effects of AFB1 on glutathione (GSH) S-transferase, Ca2+Mg2+ATPase and protein synthesis in leukocyte subpopulations, namely, mononuclear (MN) cells and polymorphonuclear (PMN) cells isolated from the blood of the domestic buffalo ( Bos bubalis), were studied. The cells were separated by using Ficoll-Paque and incubated in the presence of AFB1. GSH S-transferase activity was found to increase in cells exposed to AFB1, but there was no difference in activity between MN and PMN cells. PMN cell ATPase activity increased after AFB1 treatment, whereas no such effect was observed in the MN cells, which showed higher basal levels of ATPase activity. In the presence of AFB1, all the cells showed significant decreases in 14C-leucine incorporation, but the MN cells showed higher 14C-leucine incorporation than the PMN cells. Nevertheless, both cell types were affected by AFB1 and participated in its detoxification. There was also an appreciable decrease in the release of myeloperoxidase by activated PMN cells in the presence of AFB1.

Aflatoxin biosynthesis in Aspergillus parasiticus: effect of methionine analogs

1971 ◽  
Vol 17 (5) ◽  
pp. 569-574 ◽  
Author(s):  
R. W. Detroy ◽  
A. Ciegler
Keyword(s):  
Protein Synthesis ◽  
Aspergillus Parasiticus ◽  
Aflatoxin Production ◽  
Cellular Protein ◽  
Cellular Growth ◽  
Proliferating Cells ◽  
Group Transfer ◽  
Aflatoxin B ◽  
Transitional Phase ◽  
Methyl Group Transfer

The physiological effects of DL-ethionine and related methionine analogs upon cellular protein synthesis and methyl group transfer to aflatoxin B1 in Aspergillus parasiticus were examined in growing and resting cell systems. The addition of DL-ethionine (0.02 M) to growing mycelia inhibits cellular growth some 37% after 120 h of development. Addition of ethionine before 50 h prevents any aflatoxin synthesis; however, addition of ethionine after aflatoxin production begins has little effect upon continued synthesis. The enzymes responsible for aflatoxin production are made during the transitional phase of growth (50–70 h). During this period, ethionine administration blocks protein synthesis (measured by 14C-methionine incorporation) 85% and prevents aflatoxin synthesis. Since exogenous ethionine (3.2 mM) inhibits aflatoxin B1 synthesis about 50%, a competitive-type inhibition is indicated. Such inhibition is accompanied by the formation of a new aflatoxin B1 derivative. The incorporation of 14C-ethyl-ethionine into this derivative indicates a transethylation of the toxin ring system in the formation of ethoxy-aflatoxin B1. The addition of DL-ethionine and S-ethylcysteine to proliferating cells yields some of the aflatoxin B1 derivative.

Respiratory energy requirements and rate of protein turnover in vivo determined by the use of an inhibitor of protein synthesis and a probe to assess its effect

1994 ◽  
Vol 92 (4) ◽  
pp. 585-594 ◽  
Author(s):  
T. J. Bouma ◽  
R. De Visser ◽  
J. H. J. A. Janssen ◽  
M. J. De Kock ◽  
P H. Van Leeuwen ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Energy Requirements ◽  
Inhibitor Of Protein Synthesis
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