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Isolation and properties of a feruloyl esterase from Aureobasidium pullulans and its mechanism in lignocellulose degradationRumbold, Karl, 1973- 12 1900 (has links)
Dissertation (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The production, purification and functional characterisation of feruloyl
esterase from Aureobasidium pullulans were set as the primary objectives of
this study. A further objective was to investigate a possible co-operative effect
with other selected lignocellulolytic enzymes on substrates relevant to
industry.
In a comprehensive review, feruloyl esterases from various micro-organisms
were compared both functionally and with regard to their primary structure,
where applicable. Feruloyl esterases show intriguing differences in substrate
specificity and sequence structure. Enzymes that are closely related regarding
their amino acid sequence exhibit different substrate specificities. Sequence
similarities can be found with a range of other enzyme families, including
serine esterases, acetyl xylan esterases, lipases, tannases, glycosyl
hydrolases and xylanases. More data on the three dimensional structure of
feruloyl esterases as well as an examination of all available feruloyl esterases
with the same substrates is necessary before structure-function relationships
can be established and before the feruloyl esterases can be organized into
discrete families based on ancestral origins.
The highest production levels of feruloyl esterase by A. pullulans are achieved
when grown on birchwood xylan. Expression was not repressed when glucose
or xylose was present in the medium. However, free ferulic acid
supplemented to the medium affected fungal growth and therefore did not
increase feruloyl esterase activity. It is also suggested that the synthesis of
feruloyl esterase is independently regulated from xylanase synthesis. Feruloyl esterase from A. pullulans acts on a- and l3-naphthyl acetate, as well as
naphthol AS-D chloroacetate as substrates.
Feruloyl esterase from A. pullulans was purified to homogeneity using
ultrafiltration with high molecular weight cut-off, anion exchange, hydrophobic
interaction and ultimately gel filtration chromatography. With a molecular
weight of 210 kDa, the enzyme is the largest of the feruloyl esterases reported
to date. Kinetic data was produced using both synthetic and natural
substrates. A. pullulans feruloyl esterase shows properties similar to other
fungal feruloyl esterases, especially from Aspergillus niger cinnamic acid
esterase and Penicillium funiculosum feruloyl esterase B. The N-terminal
sequence of A. pullulans feruloyl esterase was identified, but no similarities to
known enzyme families were found. Peptide mass mapping did not reveal
structural information.
In an effort to evaluate the significance of feruloyl esterase from A. pullulans
in the degradation of lignocellulose, dissolving pulp and sugar cane bagasse
were selectively treated using feruloyl esterase and hemicellulolytic enzymes.
The enzymatic degradation reaction was monitored using microdialysis
sampling, anion exchange chromatography, online desalting and mass
spectrometry. It has been shown, that feruloyl esterase activity together with
xylanase activity releases monosaccharides from both substrates. Sugars of
higher degree of polymerisation were not released, giving evidence for the
recalcitrance of the material. The fibre architecture of the substrates was
apparently not accessible to the enzymes and therefore complete hydrolysis
was hindered. / AFRIKAANSE OPSOMMING: Die produksie, suiwering en funksionele karakterisering van feruloïel esterase
afkomstig van Aureobasidium pullulans was die primêre doelwitte van hierdie
studie. 'n Verdere doelwit was om vas te stelof daar 'n kooperatiewe effek
met ander geselekteerde lignosellulitiese ensieme op substrate wat industrierelevant
is, bestaan.
Die feruloïel esterase van verskillende mikro-organismes is vanuit die oogpunt
van funksie en primêre struktuur omvattend met mekaar vergelyk, waar
toepaslik. Interessante verskille tussen die substraat spesifisiteit en volgordestruktuur
van feruloïel esterase kan waargeneem word. Ensieme wat nou
aanmekaar verwant is wat hul aminosuurvolgorde betref, het duidelik
verskillende substraatspesifiteite. Volgordeverwantskap kan in 'n reeks van
ander ensiemfamilies, insluitende serienesterase, asetielxilaanesterase,
lipases, tannases, glikosielhidrolases en xilanases vasgestel word. Meer
inligting oor die driedimensionele struktuur van feruloïel esterase asook 'n
analise van al die beskikbare feruloïel esterase met dieselfde substrate is
nodig voordat struktuur-funksie verwantskappe vasgestel kan word en voordat
die feruloïel esterases in eie families op die grond van huloorsprong
georganiseer kan word.
Die hoogste produksie vlakke deur feruloïel esterase van A. pullulans word
bekom deur dit op berkhoutxilaan te groei. Ekspressie was nie onderdruk
wanneer glukose of xilose in die medium aanwesig was nie. Wanneer vrye
feruliensuur by die medium bygevoeg is, is die fungale groei beïnloed en het
die feruloïel esterase aktiwiteit nie vermeerder nie. Dit word ook voorgestel dat die sintese van feruloïel esterase onafhanklik deur xilanase sintese
gereguleer word. Feruloïel esterase van A. pullulans reageer op a- en f3-
naftolasetaat, asook naftol AS-D chloroasetaat as substrate. Feruloïel
esterase van A. pullulans is tot homogeniteit deur ultrafiltrering met .n hoë
molekulêre gewiggrens, anioonuitruiling, hidrofobiese interaksie en eindelik
gelfiltrasie-chromatografie gesuiwer. Met 'n molekulêre gewig van 210 kDa, is
die ensiem die grootste van die feruloïel esterases tot dusver beskryf.
Kinetiese data is met behulp van sintetiese en natuurlike substrate
geproduseer. A. pullulans feruloïel esterase het eienskappe wat vergelykbaar
is aan die van ander fungal feruloïel esterases, veral die wat afkomstig is van
Aspergillus niger sinnamiensuur esterase en Penicillium funiculosum feruloïel
esterase B. Die N-terminale volgorde van A. pullulans feruloïel esterase is
identifiseer maar geen ooreenkoms aan bekende ensiemfamilies kon
vasgestel word nie. Peptiedmassakaartering kon ook geen strukturele inligting
gee nie.
Oplosbare pulp en suikerrietbagasse is geselekteerd met behulp van feruloïel
esterase en lignosellulitiese ensieme behandel om die belang van feruloïel
esterase van A. pullulans in die afbraak van lignosellulose vas te stel. Die
hidroliese-reaksie is deur mikrodialise monsterneming, anioonuitruilingschromatografie,
oplyn ontsouting en massaspektrometrie gemonitor. Wanneer
die aktiwiteit van feruloïel esterase met die van xilanase gekombineer is, is
monosakkariede deur albei substrate afgeskei. Suikers met 'n hoër graad van
polimerisering is nie afgeskei nie, wat 'n bewys van die materiaal se
weerstandbiedendheid is. Dit het geblyk asof die vesel-argitektuur van die verbruikte substraat nie toeganklik was vir ensieme nie en dus is algehele
hidroliese verhinder.
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The reliability of esterase patterns in the determination of species of insects in the order CollembolaHart, John William January 1978 (has links)
Polyacrylamide gel electrophoresis was used to study B-esterases (EC 3.1.1.1) and C-esterases (EC 3.1.1.6) in five species of Collembola--; Folsomia candida, Proisotoma vesiculata, H,ypogastrura denticulata, and two undescribed species of Isotoma,. Ef values were computed for zymograms of 105 individuals and compared both within and among species. Certain bands-three to six in number--predominated on the zymograms of each species. The predominating bands differed among the five species resulting in a unique zymogram for each.It was also found that zymograms of normal and ecomorphic forms of Proisotoma vesiculata were dissimilar. Zymograms of specimens of Folsomia candida with access to food and those without food for 48 and 72 hours were similar. Zymograms from mascerated specimens frozen in buffer were not satisfactory.
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The use of enzymatic kinetic and dynamic kinetic resolutions in organic synthesisHaughton, Helen-Louise January 2000 (has links)
No description available.
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Histochemical study of an esterase and a "Tween" lipase in arteries and other tissues under the influence of certain factors related to atherosclerosisOrchard, Reynold Graham January 1970 (has links)
Nonspecific esterase, and in some cases a "Tween" lipase, were investigated histochemically in arteries and several other tissues of rats and rabbits under various conditions known to affect the development of atherosclerosis: age and sex differences, endocrine and metabolic factors (sex steroids, thyroid function, alloxan diabetes, and fasting), arterial injury, and acute and chronic lipemia. A study of the above enzymes was also made in atherosclerotic rabbit and human aortae.
Of the several nonvascular tissues studied, only the enzymes of the male gonads and a male accessory sex organ (the prostate) were influenced by some of the experimental conditions tested: maturation greatly increased the activity of both enzymes in the Leydig cells of the testis, and stilbestrol markedly diminished the esterase activity in the prostate epithelium. Thus, in certain reproductive organs, the enzymes reflected the functional state of the cells under investigation.
The following findings were made concerning the enzymes of the arterial wall:
1. Neither of the enzymes was influenced by ageing or sex difference in the rat, rabbit or human.
2. Neither of the enzymes was influenced by sex hormones, acute or chronic lipemia, or any of the metabolic conditions studied in the rat.
3. Esterase disappeared from the foci of acute arterial injury induced by Calciferol treatment in the rat and did not reappear six weeks after infliction of the injury.
4. Strong esterase activity appeared in the cytoplasm of lipo-phages within both human and experimental rabbit atherosclerotic lesions, in contrast to the normal arterial wall which exhibited no esterase activity at all in either species with the methods used.
5. Esterase was absent from the superficial fibrous cap of the human atherosclerotic lesion.
It is concluded that:
In the rat arteries, which normally exhibit appreciable esterolytic activity, this enzyme appears to be quite stable since it is not visibly modified by ageing or a series of endocrine and metabolic influences; it is, however, drastically diminished by acute vascular injury and this may account, at least in part, for the well known preferential accumulation of lipids in foci of acute arterial damage.
In the rabbit arteries, which normally exhibit no histochemically demonstrable esterase, appreciable esterolytic activity appears only within the cytoplasm of cells that have taken up lipid after exposure to chromic lipemia (foam cells of atheromata). Similarly, in human atheromata esterase appeared only in foam cells and was absent from the fibrous cap of the atherosclerotic lesions; thus the absence of lipid from the cap cannot be attributed to increased enzyme activity in this part of the lesion. / Medicine, Faculty of / Pathology and Laboratory Medicine, Department of / Graduate
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Macrolide resistance mechanisms in Enterobacteriaceae: Focus on azithromycinGomes, Cláudia, Martínez Puchol, Sandra, Palma, Noemí, Horna, Gertrudis, Ruiz-Roldán, Lidia, Pons, Maria J, Ruiz, Joaquim 27 October 2016 (has links)
From its introduction in 1952 onwards, the clinical use of macrolides has been steadily increasing,
both in human and veterinary medicine. Although initially designed to the treatment of Grampositive
microorganisms, this antimicrobial family has also been used to treat specific Gram-negative
bacteria. Some of them, as azithromycin, are considered in the armamentarium against
Enterobacteriaceae infections. However, the facility that this bacterial genus has to gain or
develop mechanisms of antibiotic resistance may compromise the future usefulness of these antibiotics
to fight against Enterobacteriaceae infections. The present review is focused on the mechanisms
of macrolide resistance, currently described in Enterobacteriaceae.
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Discovery and Characterization of Microbial Esterases for Fiber ModificationWang, Lijun 03 January 2011 (has links)
Carboxyl esterases, particularly arylesterases, were predicted from 16 microbial genomes, and then expressed in E. coli. Of the more than 175 cloned genes, 86 were expressed in soluble form. These were screened for activity using a range of both commercial and natural substrates. Forty-eight proteins were active on pNP-acetate at pH 8 whereas 38 proteins did not exhibit any
activity towards any substrates. Among the 48 active proteins, 20 proteins showed arylesterase activity. To date, 8 bacterial esterases and 2 archaeal arylesterases were characterized in terms of pH stability and optima, thermal inactivation, solvent stability, and kinetics. To our knowledge there is only one other published report of arylesterases from archaea. The synthetic capability
of arylesterases can transform phenolic acids to value-added chemicals. Accordingly, this project provides an arsenal of industrially significant activities that can extend the antioxidant properties of lignin-derived molecules in a broader range of renewable products.
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Discovery and Characterization of Microbial Esterases for Fiber ModificationWang, Lijun 03 January 2011 (has links)
Carboxyl esterases, particularly arylesterases, were predicted from 16 microbial genomes, and then expressed in E. coli. Of the more than 175 cloned genes, 86 were expressed in soluble form. These were screened for activity using a range of both commercial and natural substrates. Forty-eight proteins were active on pNP-acetate at pH 8 whereas 38 proteins did not exhibit any
activity towards any substrates. Among the 48 active proteins, 20 proteins showed arylesterase activity. To date, 8 bacterial esterases and 2 archaeal arylesterases were characterized in terms of pH stability and optima, thermal inactivation, solvent stability, and kinetics. To our knowledge there is only one other published report of arylesterases from archaea. The synthetic capability
of arylesterases can transform phenolic acids to value-added chemicals. Accordingly, this project provides an arsenal of industrially significant activities that can extend the antioxidant properties of lignin-derived molecules in a broader range of renewable products.
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Characterization of NonR, an esterase that confers nonactin resistanceCox, James E., January 2004 (has links)
Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xiii, 196 p.; also includes graphics (some col). Includes abstract and vita. Advisor: Robert W. Bruegemeier, Dept. of Pharmacy. Includes bibliographical references (p. 176-196).
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Development of a mouse model to study the role of paraoxonase (PON1) in organophosphate detoxication /Li, Wan-Fen. January 1999 (has links)
Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 83-102).
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A study of soy bean esterase ...Leonard, John Morrison, January 1941 (has links)
Thesis (Ph. D.)--Catholic University of America, 1941. / Reproduced from type-written copy. Description based on print version record. Bibliography: p. 76-81.
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