scholarly journals A novel enzyme activity involving the demethylation of specific partially methylated oligogalacturonides

2002 ◽  
Vol 367 (2) ◽  
pp. 511-515 ◽  
Author(s):  
Martin A.K. WILLIAMS ◽  
Jacques A.E. BENEN
Keyword(s):  
Enzyme Activity ◽  
Methyl Ester ◽  
Aspergillus Niger ◽  
Large Scale ◽  
Pectin Methylesterase ◽  
Commercial Sample ◽  
Enzymic Digestion ◽  
Primary Products ◽  
Polymeric Substrates ◽  
Partially Methylated

Studies of the enzymic digestion of pectic substrates using different polygalacturonase (PG) preparations have revealed evidence for a previously unreported enzyme activity carried out by a contaminating enzyme in one of the preparations. This observed activity involves the demethylation of specific oligogalacturonides, namely 2-methyltrigalacturonic acid and 2,3-dimethyltetragalacturonic acid. However, no large-scale demethylation of highly methylated polymeric substrates is found, demonstrating that the enzyme responsible is not a conventional pectin methylesterase (PME). Furthermore, it has been shown that a commercial sample of fungal PME from Aspergillus niger demethylates all of the oligogalacturonides present as primary products of endo-PG digestion, in contrast with the activity observed here. On the basis of the known methyl ester distribution of the endo-PG-generated fragments and knowledge of which of these oligogalacturonides are demethylated, it is concluded that the observed activity can be explained by the existence of an exo-acting methylesterase that attacks the non-reducing end of the oligogalacturonide molecules.

scholarly journals PRODUCTION OF LACCASE BY FUNGI ISOLATED FROM SOIL VIA SUBMERGED FERMENTATION USING CORN COB AS SUBSTRATE

2020 ◽  
Vol 4 (3) ◽  
pp. 224-229
Author(s):  
A. Nuhu ◽  
Ibrahim Hussaini ◽  
S. Gide ◽  
G. Anas ◽  
A. Madika
Keyword(s):  
Enzyme Activity ◽  
Aspergillus Niger ◽  
Large Scale ◽  
Fungal Species ◽  
Soil Samples ◽  
Potato Dextrose Agar ◽  
Laccase Production ◽  
Corn Cob ◽  
Fungal Isolates ◽  
Fusarium Sp

One of the limitations of large scale application of laccase (EC 1.10.3.2) is the inability to produce them in large quantity at an affordable cost. This study was carried out to screen indigenous fungi for their ability to produce laccase using the locally available substrate. Five soil samples were collected and diluted serially, 0.1 mL of the 10-5 and 10-6 dilutions were inoculated onto Potato dextrose agar (PDA) plates. The fungal isolates were identified based on their macroscopic and microscopic characteristics. The isolates were then screened for laccase production by growing them on PDA containing tannic acid as an indicator compound. The laccase producing isolates were further screened for their ability to utilize corn cob as a substrate for laccase production. Ten fungal species were isolated and identified as Trichoderma viridae (3), Trichoderma harzianum (3), Aspergillus niger (2), Fusarium sp. (1) and Penicillium sp. (1). Only two of the isolates namely T. viridae and T. harzianum were found to be laccase producers. Both laccase producing fungal species were able to utilize corn cob as substrate for laccase production. T. viridae had higher enzyme activity (2.228 U/mL) than T. harzianum (2.1583 U/mL) after 9 days of incubation. Laccase producing fungi were isolated in this study and they were able to use corn cob as substrate for laccase production.

scholarly journals Partially esterified oligogalacturonides are the preferred substrates for pectin methylesterase of Aspergillus niger

2003 ◽  
Vol 372 (1) ◽  
pp. 211-218 ◽  
Author(s):  
Gert-Jan W. M. van ALEBEEK ◽  
Katrien van SCHERPENZEEL ◽  
Gerrit BELDMAN ◽  
Henk A. SCHOLS ◽  
Alphons G. J. VORAGEN
Keyword(s):  
Methyl Ester ◽  
Aspergillus Niger ◽  
Methyl Esters ◽  
Pectin Methylesterase ◽  
Degree Of Polymerization ◽  
Specific Pattern ◽  
Specific Product ◽  
Ionization Time ◽  
Active Site Cleft

Investigations on the mode of action of Aspergillus niger pectin methylesterase (PME) towards differently C6- and C1-substituted oligogalacturonides (oligoGalpA) are described. De-esterification of methyl-esterified (un)saturated oligoGalpA proceeds via a specific pattern, depending on the degree of polymerization. Initially, a first methyl ester of the oligomer is hydrolysed, resulting in one free carboxyl group. Subsequently, this first product is preferred as a substrate and is de-esterified for a second time. This product is then accumulated and hereafter de-esterified further to the final product, i.e. oligoGalpA containing one methyl ester located at the non-reducing end residue for both saturated and unsaturated oligoGalpA, as found by post-source decay matrix-assisted laser-desorption/ionization–time-of-flight MS. The saturated hexamer is an exception to this: three methyl esters are removed very rapidly, instead of two methyl esters. When unsaturated oligoGalpA were used, the formation of the end product differed slightly, suggesting that the unsaturated bond at the non-reducing end influences the de-esterification process. In vivo, PME prefers methyl esters, but the enzyme appeared to be tolerant for other C6- and C1-substituents. Changing the type of ester (ethyl esterification) or addition of a methyl glycoside (C1) only reduced the activity or had no effect respectively. The specific product pattern was identical for all methyl- and ethyl-esterified oligoGalpA and methyl-glycosidated oligoGalpA, which strongly indicates that one or perhaps two non-esterified oligoGalpA are preferred in the active-site cleft.

scholarly journals Integration of enzyme constraints in a genome-scale metabolic model of Aspergillus niger improves phenotype predictions

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Jingru Zhou ◽  
Yingping Zhuang ◽  
Jianye Xia
Keyword(s):  
Aspergillus Niger ◽  
Large Scale ◽  
Measurement Techniques ◽  
Metabolic Model ◽  
System Level ◽  
Metabolic Phenotype ◽  
Omics Data ◽  
Prediction Ability ◽  
Phenotype Prediction ◽  
Genome Scale

Abstract Background Genome-scale metabolic model (GSMM) is a powerful tool for the study of cellular metabolic characteristics. With the development of multi-omics measurement techniques in recent years, new methods that integrating multi-omics data into the GSMM show promising effects on the predicted results. It does not only improve the accuracy of phenotype prediction but also enhances the reliability of the model for simulating complex biochemical phenomena, which can promote theoretical breakthroughs for specific gene target identification or better understanding the cell metabolism on the system level. Results Based on the basic GSMM model iHL1210 of Aspergillus niger, we integrated large-scale enzyme kinetics and proteomics data to establish a GSMM based on enzyme constraints, termed a GEM with Enzymatic Constraints using Kinetic and Omics data (GECKO). The results show that enzyme constraints effectively improve the model’s phenotype prediction ability, and extended the model’s potential to guide target gene identification through predicting metabolic phenotype changes of A. niger by simulating gene knockout. In addition, enzyme constraints significantly reduced the solution space of the model, i.e., flux variability over 40.10% metabolic reactions were significantly reduced. The new model showed also versatility in other aspects, like estimating large-scale $$k_{{cat}}$$ k cat values, predicting the differential expression of enzymes under different growth conditions. Conclusions This study shows that incorporating enzymes’ abundance information into GSMM is very effective for improving model performance with A. niger. Enzyme-constrained model can be used as a powerful tool for predicting the metabolic phenotype of A. niger by incorporating proteome data. In the foreseeable future, with the fast development of measurement techniques, and more precise and rich proteomics quantitative data being obtained for A. niger, the enzyme-constrained GSMM model will show greater application space on the system level.

Convenient Partial Purification of Glucose Oxidase from Aspergillus niger A9 Fermentation Broth by Reversed Micelles

2012 ◽  
Vol 554-556 ◽  
pp. 957-961
Author(s):  
Hong An ◽  
Xi Feng He ◽  
Shu Gang Gao
Keyword(s):  
Enzyme Activity ◽  
Aspergillus Niger ◽  
Glucose Oxidase ◽  
Fermentation Broth ◽  
Volume Ratio ◽  
Reversed Micelles ◽  
Partial Purification ◽  
Ammonium Bromide ◽  
Ultrasonic Oscillation ◽  
Protein Activity

Aim of this work was to establish the optimum conditions for the extraction and recovery by cationic reversed micelles of glucose oxidase (GOX) from Aspergillus niger A9, The influence of pH, temperature, solvent/co-solvents ratio on the extraction was investigated by experiment, using the residual enzyme activity to evaluate the results. The best condition for GOX extraction were ensured using iso-octane as solvent and butanol and n-hexanol co-solvent at 76/18/6 volume ratio, pH 4.80, 200mM cetyl-trimethyl ammonium bromide (CTAB) as cationic surfactant, The enzyme activity of GOX is measured by DNS method (3,5-dinitro salicylic acid method). In the extraction process, ultrasonic oscillation was adopted to mix organic solvent and water, ultrasonic oscillation temperature is 45 °C. Protein activity recovery of GOX can reach 88.2% in extraction.

scholarly journals Produksi Enzim Selulase olehAspergillus niger pada Ampas Sagu

2015 ◽  
Vol 16 (1) ◽  
pp. 1 ◽  
Author(s):  
Nora Idiawati ◽  
Elliska Murni Harfinda ◽  
Lucy Arianie
Keyword(s):  
Enzyme Activity ◽  
Aspergillus Niger ◽  
Moisture Content ◽  
Cellulase Enzymes ◽  
Fermentation Time ◽  
Cellulase Enzyme ◽  
Sago Waste ◽  
Solid Fermentation

Production of cellulase by Aspergillus niger was carried out by growing the cultureson sago waste. Sago waste containscellulose that has not been used optimally. Cellulose is a polysaccharide consisting of glucose monomers linked by β-1,4-glycosides bonds. Glycoside bonds in cellulose can be enzymatically hydrolyzed into glucose with cellulase enzymes. Solid fermentation used to produce cellulase on sago waste as substrate was influenced by pH (3 to 6), moisture content(40% to 85%), and fermentation time (4 to 10 days). Products of the cellulase enzyme activity was measured by phenolsulfuricacid method. The results showed that the highest cellulase enzyme activity was 0.172 U/mL obtained at 85%moisture content, pH 5, and 8 days of fermentation time.

scholarly journals Enzyme activity in the micropylar region of Melanoxylon brauna Schott seeds during germination under heat stress conditions

2020 ◽  
Vol 42 ◽  
Author(s):  
Marcone Moreira Santos ◽  
Eduardo Euclydes de Lima e Borges ◽  
Glauciana da Mata Ataíde ◽  
Raquel Maria de Oliveira Pires ◽  
Debora Kelli Rocha
Keyword(s):  
Enzyme Activity ◽  
Heat Stress ◽  
Seed Germination ◽  
Pectin Methylesterase ◽  
Stress Conditions ◽  
Southeastern Brazil ◽  
Experimental Conditions ◽  
Mannanase Activity ◽  
Ecological Importance ◽  
The Many

Abstract: Recent studies indicate that global temperatures will rise substantially in the 21st century, leading to the extinction of several plant species, as plant metabolism and germination are greatly affected by temperature. Melanoxylon brauna, a tree species native to the Atlantic Forest that occurs from northeastern to southeastern Brazil, is one of the many species threatened by global warming. Despite the economic and ecological importance of M. brauna, studies investigating the influence of heat stress on seed germination and biochemical responses are still incipient. This study aimed to evaluate enzyme activity in the micropylar region of M. brauna seeds during germination under heat stress conditions. Endo-β-mannanase, α-galactosidase, polygalacturonase, pectin methylesterase, pectin lyase, total cellulase, 1,3-β-glucosidase, and 1,4-β-glucosidase activities were determined in micropyles of seeds imbibed for 24, 48 and 72 h at 25, 35 and 45 °C. Seed germination was highest at 25 °C. Endo-β-mannanase activity was not detected under any of the experimental conditions, but imbibition temperature had a significant effect on the activity of all other enzymes.

scholarly journals Coupled structural transitions enable highly cooperative regulation of human CTPS2 filaments

2019 ◽  
Author(s):  
Eric M. Lynch ◽  
Justin M. Kollman
Keyword(s):  
Enzyme Activity ◽  
Active Sites ◽  
Large Scale ◽  
Conformational State ◽  
Ctp Synthase ◽  
Widespread Phenomenon ◽  
And Control ◽  
Allosteric Regulators ◽  
Low Activity

Many enzymes assemble into defined oligomers, providing a mechanism for cooperatively regulating enzyme activity. Recent studies in tissues, cells, and in vitro have described a mode of regulation in which enzyme activity is modulated by polymerization into large-scale filaments1–5. Enzyme polymerization is often driven by binding to substrates, products, or allosteric regulators, and tunes enzyme activity by locking the enzyme in high or low activity states1–5. Here, we describe a unique, ultrasensitive form of polymerization-based regulation employed by human CTP synthase 2 (CTPS2). High-resolution cryoEM structures of active and inhibited CTPS2 filaments reveal the molecular basis of this regulation. Rather than selectively stabilizing a single conformational state, CTPS2 filaments dynamically switch between active and inactive filament forms in response to changes in substrate and product levels. Linking the conformational state of many CTPS2 subunits in a filament results in highly cooperative regulation, greatly exceeding the limits of cooperativity for the CTPS2 tetramer alone. The structures also reveal a link between conformational state and control of ammonia channeling between the enzyme’s two active sites. This filament-based mechanism of enhanced cooperativity demonstrates how the widespread phenomenon of enzyme polymerization can be adapted to achieve different regulatory outcomes.

Expression and characterization of a pectin methylesterase from Aspergillus niger ZJ5 and its application in fruit processing

2018 ◽  
Vol 126 (6) ◽  
pp. 690-696 ◽  
Author(s):  
Zhiwei Zhang ◽  
Junshuai Dong ◽  
Deqing Zhang ◽  
Jiaojiao Wang ◽  
Xing Qin ◽  
...  
Keyword(s):  
Aspergillus Niger ◽  
Pectin Methylesterase ◽  
Fruit Processing
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