The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Peter G. Mantle - One of the best experts on this subject based on the ideXlab platform.
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Biosynthesis of ochratoxins by Aspergillus ochraceus.
Phytochemistry, 2001Co-Authors: Jonathan P Harris, Peter G. MantleAbstract:Abstract Shaken liquid fermentation of an isolate of Aspergillus ochraceus showed growth-associated production of ochratoxins A and B, followed by production of a related polyketide diaporthin. Later, between 150 and 250 h, mellein accumulated transitorily. In contrast, shaken solid substrate (shredded wheat) fermentation over 14 days produced mainly ochratoxins A and B (ratio ca. 5:1) in very high yield (up to 10 mg/g). In these systems experiments with 14 C-labelled precursors and putative intermediates revealed temporal separation of early and late stages of the ochratoxin biosynthetic pathway, but did not support an intermediary role for mellein. The pentaketide intermediate ochratoxin β was biotransformed very efficiently into both ochratoxins A and B, 14 and 19%, respectively. The already chlorinated ochratoxin α was only biotransformed significantly (4.85%) into ochratoxin A, indicating that chlorination is mainly a penultimate biosynthetic step in the biosynthesis of ochratoxin A. This was supported by poor (1.5%) conversion of radiolabelled ochratoxin B into ochratoxin A. Experiments implied that some ochratoxin B may arise by dechlorination of ochratoxin A.
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Biosynthesis of diaporthin and orthosporin by Aspergillus ochraceus.
Phytochemistry, 2001Co-Authors: Jonathan P Harris, Peter G. MantleAbstract:Diaporthin and orthosporin were characterised from the fungus Aspergillus ochraceus D2306. Diaporthin was identified by high-resolution electron impact mass spectrometry and 1H and 13C NMR spectroscopy, from which new spectroscopic assignments were made. Orthosporin was also identified by mass spectrometry and both fungal metabolites are reported for the first time as co-metabolites and also as products of A. ochraceus. The methylation inhibitor ethionine affected production of both diaporthin and orthosporin in spite of no obvious methylation step in the biosynthesis of orthosporin, implying that extracellular orthosporin may arise by de-O-methylation of diaporthin. The biosynthetic origin of diaporthin was demonstrated by incorporation of [1-14C]acetate and [methyl-14C]methionine administered in early idiophase.
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Influence of halogen salts on the production of the ochratoxins by Aspergillus ochraceus Wilh.
Journal of agricultural and food chemistry, 2000Co-Authors: Maria A. Stander, Peter G. Mantle, Pieter S. Steyn, Annelie Lübben, Ana Miljkovic, Gert J. MaraisAbstract:The first report of the biological production of bromo ochratoxin B by Aspergillus ochraceus Wilh. is presented as well as a study of the influence of potassium bromide, potassium iodide, potassium...
N S Egorov - One of the best experts on this subject based on the ideXlab platform.
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Production of proteinases with fibrinolytic and fibrinogenolytic activity by a micromycete Aspergillus ochraceus
Microbiology, 2017Co-Authors: A. A. Osmolovskiy, N A Baranova, E. D. Rukavitsyna, V. G. Kreier, N S EgorovAbstract:Fibrinolytic and fibrinogenolytic activity of surface and submerged cultures of a micromycete Aspergillus ochraceus L-1 was studied. Extracellular proteinases produced by A. ochraceus L-1 were found to exhibit specificity against fibrin and fibrinogen and no activity of plasminogen activators. The highest activity was observed in the cultures grown at 28°С and initial pH 7.0. Fibrinolytic activity was shown to be somewhat above 25% of the total plasmin-like activity of A. ochraceus L-1 proteinases.
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Properties of extracellular plasmin-like proteases of Aspergillus ochraceus micromycete
Applied Biochemistry and Microbiology, 2017Co-Authors: A. A. Osmolovskiy, N A Baranova, V. G. Kreier, N S EgorovAbstract:The properties of two extracellular proteases of Aspergillus ochraceus VKM F-4104D micromycete with plasmin-like activity have been studied. It has been shown that the enzymes differ in pI (5.05 and 6.83) and have similar molecular weights (about 32 and 35 kDa), pH optima (pH 9.0–10.00 at 45°C), and specificities of action on a limited set of chromogenic peptide substrates of trypsin-like proteases. According to inhibitory analysis, both enzymes belong to the serine proteases. Their properties appeared to be similar to those of the protease, protein C activator, which is the main proteolytic enzyme of A. ochraceus VKM F-4104D. Most likely, proteases of this micromyсetes are isoenzymes.
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Aspergillus ochraceus micromycetes—producers of extracellular proteinases—protein C activators of blood plasma
Applied Biochemistry and Microbiology, 2012Co-Authors: A. A. Osmolovskiy, N A Baranova, A V Kurakov, V. G. Kreier, N S EgorovAbstract:Natural isolates of Aspergillus ochraceus micromycetes from soil and plant remains from various regions have been screened. The isolated strains were characterized by similar cultural and morphological features and an identical nucleotide sequence in the ITS1-5,8S-ITS2 region of rDNA. The ability of the extracellular proteinases of A. ochraceus micromycetes to activate protein C of blood plasma has been established. Differences are revealed in the accumulation of proteinases activating protein C and proteinases with thrombinand plasmin-like activities in the growth dynamics of producers.
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Aspergillus ochraceus micromycetes producers of extracellular proteinases protein c activators of blood plasma
Applied Biochemistry and Microbiology, 2012Co-Authors: A. A. Osmolovskiy, N A Baranova, A V Kurakov, V. G. Kreier, N S EgorovAbstract:Natural isolates of Aspergillus ochraceus micromycetes from soil and plant remains from various regions have been screened. The isolated strains were characterized by similar cultural and morphological features and an identical nucleotide sequence in the ITS1-5,8S-ITS2 region of rDNA. The ability of the extracellular proteinases of A. ochraceus micromycetes to activate protein C of blood plasma has been established. Differences are revealed in the accumulation of proteinases activating protein C and proteinases with thrombinand plasmin-like activities in the growth dynamics of producers.
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Aspergillus ochraceus myxomycetes produce extracellular proteinases--protein C activators of blood plasma
Prikladnaia biokhimiia i mikrobiologiia, 2012Co-Authors: A A Osmolovskiĭ, V G Kreĭer, A V Kurakov, N A Baranova, N S EgorovAbstract:Natural isolates of Aspergillus ochraceus myxomycetes from soil and plant remains from various regions have been screened. The isolated strains were characterized by similar cultural and morphological features and an identical nucleotide sequence in the ITS1-5,8S-ITS2 region of rDNA. The ability of the extracellular proteinases of A. ochraceus myxomycetes to activate protein C of blood plasma has been established. Differences are revealed in the accumulation of proteinases activating protein C and proteinases with thrombin- and plasmin-like activities in the growth dynamics of producers.
Timir B. Samanta - One of the best experts on this subject based on the ideXlab platform.
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Bioconversion of progesterone by the activated immobilized conidia of Aspergillus ochraceus TS.
Current microbiology, 1999Co-Authors: Tapan K. Dutta, Timir B. SamantaAbstract:Progesterone was transformed to its 11α-hydroxy derivative (100% e.e) by the activated immobilized conidia of Aspergillus ochraceus TS. The immobilized preparation retained 79% of free conidial activity. The immobilized conidia, activated by nutrients, exhibited an increase in 11α-hydroxylation, and it was free of the side product 6β, 11α-dihydroxy progesterone. The half life and turnover of immobilized and activated immobilized conidia were 14 and 12 days and 187 and 416 μmoles of the product/g of conidia respectively. The pH and temperature profiles of the free conidia remained unaltered after immobilization and activation. Some germination of conidia inside the matrix owing to incubation with nutrients was detected by scanning electron microscopy.
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Characterization of a novel microsomal glutathione S-transferase produced by Aspergillus ochraceus TS.
Molecular and cellular biochemistry, 1992Co-Authors: Jharna Datta, Timir B. SamantaAbstract:Purification and characterization of microsomal glutathione S-transferase produced by Aspergillus ochraceus TS are reported. The isozymes are located in microsomes and were active against 1-chloro-2,4-dinitrobenzene, ethacrynic acid, 1,2-dichloro-4-nitrobenzene, trans-4- phenyl-3-buten-2-one,p-nitrobenzyl chloride and bromosulphophthalein. They were inhibited by N-ethylmaleimide and bromosulphophthalein. The GST isozymes produced by Aspergillus ochraceus TS are indistinguishable in respect of their molecular mass both in native and denatured state. The subunit of the purified protein had an apparent Mr of 11 kDa while molecular mass of the native protein is around 56 kDa. The substrate specificity and pl values of the isozymes were different. The GSTs produced by Aspergillus ochraceus TS fairly share functional properties with mammalian cytosolic isozymes.
Jonathan P Harris - One of the best experts on this subject based on the ideXlab platform.
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Biosynthesis of ochratoxins by Aspergillus ochraceus.
Phytochemistry, 2001Co-Authors: Jonathan P Harris, Peter G. MantleAbstract:Abstract Shaken liquid fermentation of an isolate of Aspergillus ochraceus showed growth-associated production of ochratoxins A and B, followed by production of a related polyketide diaporthin. Later, between 150 and 250 h, mellein accumulated transitorily. In contrast, shaken solid substrate (shredded wheat) fermentation over 14 days produced mainly ochratoxins A and B (ratio ca. 5:1) in very high yield (up to 10 mg/g). In these systems experiments with 14 C-labelled precursors and putative intermediates revealed temporal separation of early and late stages of the ochratoxin biosynthetic pathway, but did not support an intermediary role for mellein. The pentaketide intermediate ochratoxin β was biotransformed very efficiently into both ochratoxins A and B, 14 and 19%, respectively. The already chlorinated ochratoxin α was only biotransformed significantly (4.85%) into ochratoxin A, indicating that chlorination is mainly a penultimate biosynthetic step in the biosynthesis of ochratoxin A. This was supported by poor (1.5%) conversion of radiolabelled ochratoxin B into ochratoxin A. Experiments implied that some ochratoxin B may arise by dechlorination of ochratoxin A.
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Biosynthesis of diaporthin and orthosporin by Aspergillus ochraceus.
Phytochemistry, 2001Co-Authors: Jonathan P Harris, Peter G. MantleAbstract:Diaporthin and orthosporin were characterised from the fungus Aspergillus ochraceus D2306. Diaporthin was identified by high-resolution electron impact mass spectrometry and 1H and 13C NMR spectroscopy, from which new spectroscopic assignments were made. Orthosporin was also identified by mass spectrometry and both fungal metabolites are reported for the first time as co-metabolites and also as products of A. ochraceus. The methylation inhibitor ethionine affected production of both diaporthin and orthosporin in spite of no obvious methylation step in the biosynthesis of orthosporin, implying that extracellular orthosporin may arise by de-O-methylation of diaporthin. The biosynthetic origin of diaporthin was demonstrated by incorporation of [1-14C]acetate and [methyl-14C]methionine administered in early idiophase.
Yang Liu - One of the best experts on this subject based on the ideXlab platform.
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ph signaling transcription factor aopacc regulates ochratoxin a biosynthesis in Aspergillus ochraceus
Journal of Agricultural and Food Chemistry, 2018Co-Authors: Yan Wang, Fei Liu, Liuqing Wang, Qi Wang, Jonathan Nimal Selvaraj, Yueju Zhao, Yun Wang, Fuguo Xing, Yang LiuAbstract:In Aspergillus and Penicillium species, an essential pH-response transcription factor pacC is involved in growth, pathogenicity, and toxigenicity. To investigate the connection between ochratoxin A (OTA) biosynthesis and ambient pH, the AopacC in Aspergillus ochraceus was functionally characterized using a loss-of-function mutant. The mycelium growth was inhibited under pH 4.5 and 10.0, while the sporulation increased under alkaline condition. A reduction of mycelium growth and an elevation of sporulation was observed in ΔAopacC mutant. Compared to neutral condition, OTA contents were respectively reduced by 71.6 and 79.8% under acidic and alkaline conditions. The expression of AopacC increased with the elevated pH, and deleting AopacC dramatically decreased OTA production and biosynthetic genes Aopks expression. Additionally, the ΔAopacC mutant exhibited attenuated infection ability toward pear fruits. These results suggest that AopacC is an alkaline-induced regulator responsible for growth and OTA biosy...
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arabidopsis thaliana defense response to the ochratoxin a producing strain Aspergillus ochraceus 3 4412
Plant Cell Reports, 2015Co-Authors: Junran Hao, Yan Wang, Zhuojun Yang, Yang Liu, Yanan Zhai, Jing Yang, Zhihong Liang, Kunlun HuangAbstract:OTA-producing strain Aspergillus ochraceus induc ed necrotic lesions, ROS accumulation and defense responses in Arabidopsis . Primary metabolic and defense-related proteins changed in proteomics. Ascorbate–glutathione cycle and voltage-dependent anion-selective channel proteins fluctuated. Mycotoxigenic fungi, as widespread contaminants by synthesizing mycotoxins in pre-/post-harvest infected plants and even stored commercial cereals, could usually induce plant–fungi defense responses. Notably, ochratoxin A (OTA) is a nephrotoxic, hepatotoxic, teratogenic, immunotoxic and phytotoxic mycotoxin. Herein, defense responses of model system Arabidopsis thaliana detached leaves to infection of Aspergillus ochraceus 3.4412, an OTA high-producing strain, were studied from physiological, proteomic and transcriptional perspectives. During the first 72 h after inoculation (hai), the newly formed hypersensitive responses-like lesions, decreased chlorophyll content, accumulated reactive oxygen species and upregulated defense genes expressions indicated the defense response was induced in the leaves with the possible earlier motivated jasmonic acid/ethylene signaling pathways and the later salicylic acid-related pathway. Moreover, proteomics using two-dimensional gel electrophoresis 72 hai showed 16 spots with significantly changed abundance and 13 spots corresponding to 12 unique proteins were successfully identified by MALDI-TOF/TOF MS/MS. Of these, six proteins were involved in basic metabolism and four in defense-related processes, which included glutathione-S-transferase F7, voltage-dependent anion-selective channel protein 3 (VDAC-3), osmotin-like protein OSM34 and blue copper-binding protein. Verified from proteomic and/or transcriptional perspectives, it is concluded that the primary metabolic pathways were suppressed with the ascorbate–glutathione cycle fluctuated in response to A. ochraceus and the modulation of VDACs suggested the possibility of structural damage and dysfunction of mitochondria in the process. Taken together, these findings exhibited a dynamic overview of the defense responses of A. thaliana to A. ochraceus and provided a better insight into the pathogen-resistance mechanisms in plants.
