Bibliografie tematiche / Enzymes Synthesis

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Letteratura scientifica selezionata sul tema "Enzymes Synthesis"

Autore: Grafiati
Pubblicato: 4 giugno 2021
Ultima modifica: 6 settembre 2023

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Articoli di riviste sul tema "Enzymes Synthesis"

1

Malá, Š., P. Karasová, M. Marková e B. Králová. "Oligosaccharide synthesis using a-glucosidases of different origin". Czech Journal of Food Sciences 19, No. 2 (7 febbraio 2013): 57–61. http://dx.doi.org/10.17221/6576-cjfs.

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a-Glucosidase from Aspergillus awamori and intestinal a-glucosidase (saccharase-isomaltase complex) exhibited high transglycosylation activity and were able to synthesize tri- and tetrasaccharides during maltose hydrolysis. Both tested enzymes were also able to transfer the glucose residue to all tested monosaccharide acceptors (D-mannose, D-xylose, L-sorbose and D-galactose). Their transfer activity towards respective acceptors varied and their acceptor preference also depended on the origin of the enzyme. Out of the acceptors tested, both enzymes exhibited high transfer activity in xylose.
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Herman, Richard Ansah, Xuan Zhu, Ellen Ayepa, Shuai You e Jun Wang. "Advances in the One-Step Approach of Polymeric Materials Using Enzymatic Techniques". Polymers 15, n. 3 (30 gennaio 2023): 703. http://dx.doi.org/10.3390/polym15030703.

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The formulation in which biochemical enzymes are administered in polymer science plays a key role in retaining their catalytic activity. The one-step synthesis of polymers with highly sequence-controlled enzymes is a strategy employed to provide enzymes with higher catalytic activity and thermostability in material sustainability. Enzyme-catalyzed chain growth polymerization reactions using activated monomers, protein–polymer complexation techniques, covalent and non-covalent interaction, and electrostatic interactions can provide means to develop formulations that maintain the stability of the enzyme during complex material processes. Multifarious applications of catalytic enzymes are usually attributed to their efficiency, pH, and temperature, thus, progressing with a critical structure-controlled synthesis of polymer materials. Due to the obvious economics of manufacturing and environmental sustainability, the green synthesis of enzyme-catalyzed materials has attracted significant interest. Several enzymes from microorganisms and plants via enzyme-mediated material synthesis have provided a viable alternative for the appropriate synthesis of polymers, effectively utilizing the one-step approach. This review analyzes more and deeper strategies and material technologies widely used in multi-enzyme cascade platforms for engineering polymer materials, as well as their potential industrial applications, to provide an update on current trends and gaps in the one-step synthesis of materials using catalytic enzymes.
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O'Keefe, S. J., W. M. Bennet, A. R. Zinsmeister e M. W. Haymond. "Pancreatic enzyme synthesis and turnover in human subjects". American Journal of Physiology-Gastrointestinal and Liver Physiology 266, n. 5 (1 maggio 1994): G816—G821. http://dx.doi.org/10.1152/ajpgi.1994.266.5.g816.

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Animal studies have shown that pancreatic enzyme secretion is independent of enzyme synthesis. To investigate this relationship in humans, we have coinfused 14C-labeled leucine tracer with cholecystokinin octapeptide in nine healthy adults for 4 h and measured the rate of appearance of secreted and newly labeled enzymes in the duodenum. Enzyme secretion was well maintained throughout, but newly labeled enzymes only appeared in juice between 75 and 101 min (median time, 86 min), indicating that initial secretion was dependent on the release of zymogen stores and that the median production time for new enzymes was 86 min. Between 85 and 225 min there was a curvilinear increase in the enrichment of secreted enzymes with newly synthesized enzymes, suggesting a median turnover rate of zymogen stores of 29%/h (range 12-47%/h). In conclusion, our results suggest that in healthy humans, postprandial pancreatic enzyme secretion is maintained by the export of a large stored pool and is not rate limited by enzyme synthesis, since it takes approximately 86 min for newly synthesized enzymes to take part in the digestive process.
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Juwon, Arotupin Daniel, e Ogunmolu Funso Emmanuel. "Experimental Investigations on the Effects of Carbon and Nitrogen Sources on Concomitant Amylase and Polygalacturonase Production by Trichoderma viride BITRS-1001 in Submerged Fermentation". Biotechnology Research International 2012 (15 luglio 2012): 1–8. http://dx.doi.org/10.1155/2012/904763.

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The paper investigates the effects of different commercial carbon and nitrogen sources on the concomitant synthesis of amylase and polygalacturonase enzymes with the aim of optimizing them for maximal enzyme production. The microorganism used in this work was the fungus Trichoderma viride BITRS-1001, which had been previously identified as a highly active producer of amylase and polygalacturonase enzymes. The results showed that the different commercial carbon and nitrogen substrate significantly affected the concomitant syntheses of amylase and polygalacturonase in culture media supplemented with the different commercial carbon and nitrogen substrates. The result obtained suggested that for optimal and concomitant synthesis of the enzymes by Trichoderma viride BITRS-1001 in submerged fermentation, minimal medium supplemented with maltose and casein were the carbon and nitrogen substrates of choice.
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Hu, Chong, Yunxiu Bai, Miao Hou, Yisu Wang, Licheng Wang, Xun Cao, Chiu-Wing Chan et al. "Defect-induced activity enhancement of enzyme-encapsulated metal-organic frameworks revealed in microfluidic gradient mixing synthesis". Science Advances 6, n. 5 (gennaio 2020): eaax5785. http://dx.doi.org/10.1126/sciadv.aax5785.

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Mimicking the cellular environment, metal-organic frameworks (MOFs) are promising for encapsulating enzymes for general applications in environments often unfavorable for native enzymes. Markedly different from previous researches based on bulk solution synthesis, here, we report the synthesis of enzyme-embedded MOFs in a microfluidic laminar flow. The continuously changed concentrations of MOF precursors in the gradient mixing on-chip resulted in structural defects in products. This defect-generating phenomenon enables multimodal pore size distribution in MOFs and therefore allows improved access of substrates to encapsulated enzymes while maintaining the protection to the enzymes. Thus, the as-produced enzyme-MOF composites showed much higher (~one order of magnitude) biological activity than those from conventional bulk solution synthesis. This work suggests that while microfluidic flow synthesis is currently underexplored, it is a promising strategy in producing highly active enzyme-MOF composites.
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Bur, Daniel, Marcel A. Luyten, Hla Wynn, Louis R. Provencher, J. Bryan Jones, Marvin Gold, James D. Friesen, Anthony R. Clarke e J. John Holbrook. "An evaluation of the substrate specificity and asymmetric synthesis potential of the cloned L-lactate dehydrogenase from Bacillusstearothermophilus". Canadian Journal of Chemistry 67, n. 6 (1 giugno 1989): 1065–70. http://dx.doi.org/10.1139/v89-161.

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The potential utility of the L-lactate dehydrogenase of Bacillusstearothermophilus (BSLDH) for stereospecific, preparative-scale reductions of α-keto acids to (S)-α-hydroxy acids of > 99% ee has been demonstrated. BSLDH is a stable, thermophilic, enzyme whose gene has been cloned into a high-expression vector to assure its plentiful supply. Its specificity for keto acid substrates possessing straight- and branched-chain alkyl, cyclopropyl, or phenyl groups has been evaluated in preparative and kinetic terms, and compared with that of the mammalian pig heart enzyme (PHLDH). The specificities of BSLDH and PHLDH are similar, with branched alkyl-chain keto acids being poor substrates for both enzymes. Keywords: enzymes in organic syntheses, lactate dehydrogenase, asymmetric synthesis.
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Smith, A. G. "Subcellular localization of two porphyrin-synthesis enzymes in Pisum sativum (pea) and Arum (cuckoo-pint) species". Biochemical Journal 249, n. 2 (15 gennaio 1988): 423–28. http://dx.doi.org/10.1042/bj2490423.

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The subcellular location of the two porphyrin-synthesis enzymes 5-aminolaevulinate dehydratase (ALAD) and porphobilinogen deaminase (PBGD) was investigated in Pisum sativum (pea) leaves and spadices of Arum (cuckoo-pint). Throughout the tissue-fractionation procedures the distribution of the two enzymes paralleled that of the plastid marker enzyme (ADP-glucose pyrophosphorylase), even in Arum, a tissue where the synthesis of non-plastid haem is predominant. The distribution of cytosolic marker enzyme (lactate dehydrogenase) was significantly different from that of ALAD and PBGD and, although purified mitochondria from both species had some residual activity, this was always less than contaminating plastid marker enzyme. The results suggest that ALAD and PBGD are exclusively plastid enzymes. The significance of this for the role of plastids in cellular porphyrin synthesis is discussed.
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Hai guan Ding, Hai guan Ding, Zhi qiang Cai Zhi qiang Cai, Ling Hou Ling Hou, Zhi quan Hu Zhi quan Hu, Zheng sheng Jin Zheng sheng Jin, Di Xu Di Xu, Hui Cao Miao miao Meng Hui Cao Miao miao Meng, Yu Hui Xie Yu Hui Xie e De qiang Zheng De qiang Zheng. "Synthesis and Evaluation of Some Novel 6-Substituted Quinazoline Derivatives as Antitumor Agents". Journal of the chemical society of pakistan 41, n. 1 (2019): 186. http://dx.doi.org/10.52568/000716/jcsp/41.01.2019.

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A series of novel 6-substituted quinazoline derivatives were synthesised as epidermal growth factor receptor(EGFR) and Human epidermal growth factor receptor 2 (HER2)inhibitors in our lab. The novel compounds were measured for their dual enzyme inhibition as well as their cytotoxic activity on MCF7 cell line. The results revealed that all the compounds showed inhibition of both enzymes. Compound 5c showed the best inhibitory activity against both enzymes and IC50 of its was 2.6 nM against EGFR kinases and 4.3 nM against HER2 kinases, respectively. Most of the measured compounds showed to antitumor activity on MCF7.
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Morrow, Cary J. "Biocatalytic Synthesis of Polyesters Using Enzymes". MRS Bulletin 17, n. 11 (novembre 1992): 43–47. http://dx.doi.org/10.1557/s0883769400046650.

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Plants and animals have been exploited as sources of materials for centuries but, as our ability to analyze and fractionate them has progressed, the extraordinary range of properties available from materials produced by living systems has continued to grow. Doi, in another article in this issue of the MRS Bulletin, presents a discussion of a group of naturally occurring polyesters related to poly(beta-hydroxybutyrate). These polyesters are formed in vivo by several microorganisms as part of an energy storage scheme. Research on these systems has allowed growth conditions to be found that can lead, in a controlled fashion, to a number of copolymers. Useful materials based on these bacterial polyesters appear to be at hand.The in-vivo formation of polyesters in microorganisms also illustrates several of the important reasons for examining biocatalytic polymer synthesis. First, unlike most industrial syntheses of polyesters, the poly(beta-hydroxybutyrate) biosynthesis occurs at a near-ambient temperature using a carbohydrate feedstock. Second, and perhaps most importantly, the stored polyesters are readily biodegraded by the bacteria that manufacture them, so materials based on these polyesters should also be biodegradable. Third, although there are side chains along the polymer backbone, they are introduced in a highly stereo-specific fashion during in-vivo synthesis, leading to an entirely stereoregular polyester. However, along with these advantages, there are also significant limitations to bacterial polyester synthesis. First, there are some substrates that are not incorporated into the polyester by the bacteria. Second, normal metabolism leads to the polyester, always incorporating a fraction of hydroxybutyrate monomers. Third, the backbone is always comprised of four-atom, A-B type 3-hydroxy acid repeat units with variations appearing in the side chain at carbon-3.
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Wong, Chi-Huey. "Enzymes for Glycoprotein Synthesis". CHIMIA International Journal for Chemistry 63, n. 6 (24 giugno 2009): 318–26. http://dx.doi.org/10.2533/chimia.2009.318.

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Tesi sul tema "Enzymes Synthesis"

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Ekici, Özlem Doğan. "Design, synthesis, and evaluation of novel irreversible inhibitors for caspases". Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04062004-164633/unrestricted/ekici%5Fozlem%5Fd%5F200312%5Fphd.pdf.

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Ekici, Ozlem Dogan. "Design, synthesis, and evaluation of novel irreversible inhibitors for caspases". Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5333.

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Naylor, Neil J. "Biotransformations involving hydrolytic enzymes". Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263607.

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Silveira, Alvito J. "Synthesis of 6-guanidinobenzoxazinones as potential inhibitors of trypsin-like enzymes". Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/26914.

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Snider, Catherine E. "Synthesis and biochemical evaluation of irreversible inhibitors of aromatase /". The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487266362338344.

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Carnell, Andrew John. "Cycloalkanone monooxygenase enzymes in organic synthesis". Thesis, University of Exeter, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293971.

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Blum, Janna Karen. "Broadening the enyzme-catalyzed synthesis of semi-synthetic antibiotics". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39528.

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An alpha-amino ester hydrolase (AEH) applicable to synthesis of semi-synthetic antibiotics was cloned from the genomic DNA of Xanthomonas campestris pv. campestris sp. strain ATCC 33913. AEHs catalyze the synthesis and hydrolysis of alpha-amino beta-lactam antibiotics. The enzyme was characterized for thermodynamic and kinetic parameters. The enzyme shows optimal ampicillin hydrolytic activity at 25C and pH 6.8. The AEH enzymes have been shown to have excellent synthetic capability. Additionally, we demonstrated the first fully aqueous enzymatic one-pot synthesis of ampicillin direct from the natural product penicillin G eliminating the isolation of the intermediate 6-APA. Lastly, to improve the thermostability of the AEH a modified structure-guided consensus model of seven homologous enzymes was generated along with analysis of the B-factors from the available crystal structures of the known AEH from Xanthomonas citri. Our best variant, which is a quadruple mutant, E143H/A275P/N186D/V622I, which has a T_50_30, the temperature at which the half-life is 30 minutes, of 34C and 1.3-fold activity compared to wild-type. Overall, we have successfully improved the understanding of the AEH class of enzymes and applied a novel cascade application, demonstrating AEHs unique applicability in the synthesis of beta-lactam antibiotics. The improved thermostability will further improve the industrial relevance of AEHs.
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Admans, Gary David. "Asymmetric transformations catalysed by lipase enzymes". Thesis, University of Exeter, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240288.

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Chambers, Martina Natasha. "Synthesis of cellulosic glycolipids using engineered enzymes". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46032.

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Cellulose, a linear polymer of D-glucose units connected by β-1,4 glycosidic bonds, adopts a highly-ordered crystalline structure in solution. In cellulose I, the dominant form of cellulose in nature, the polymeric chains are aligned in the same direction. Previous attempts to synthesize cellulose I in vitro have resulted in the synthesis of cellulose II, which has the thermodynamically favored anti-parallel orientation of chains. The synthesis of soluble fragments or defined surfaces of cellulose I would enable more detailed study of carbohydrate binding domains and other proteins that interact with cellulose in nature. The objective of this thesis is to prepare a crystalline surface of cellulose I in a controlled manner through the alignment of cellulolipids. A major focus of this thesis is the synthesis of cellulolipids with a cellohexaosyl head group. Cellohexaose is the shortest cello-oligosaccharide with cellulosic properties, but is consequently insoluble in aqueous solution. To improve the solubility of cellohexaose, the addition of a removable charged functionality was explored: either a terminal sialic acid or a phosphate group at the 6 position of the non-reducing terminal glucose. Abg2F6 glycosynthase from Agrobacterium sp. was used to synthesize β-1,4 linked cello-oligosaccharide fluorides from DP = 2 to DP = 4. These cello-oligosaccharides were modified with a removable charged functionality and utilized as donor substrates by CelB glycosynthase, a mutant of a β-1,4 endoglucanase from Caldicellulosiruptor saccharolyticus. Through the combination of glycosynthase enzymes and charged functionalities, a variety of soluble cellohexaosyl analogs were synthesized. Lyso-glycosphingolipids were prepared by transferring cello-oligosaccharyl fluorides to D-erythro-C18-sphingosine using EGCase glycosynthase. CelB glycosynthase used charged glycosyl fluoride donors to extend the lyso-glycosphingolipids, yielding soluble cellulolipids. The soluble cellulolipids were aligned along an aqueous:organic interface and the charged functionality was removed. Thus, a surface was prepared that appeared to interact with a carbohydrate binding module functionalized with a fluorescent tag. The soluble cellulolipids were successfully incorporated into a nanodisc, as shown through the incorporation of phosphorylated cellohexaosyl sphingosine. Cleavage of the phosphate using alkaline phosphatase yielded a nanodisc containing cellulolipids.
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Ahmed, Naveed. "The synthesis of inhibitors of proteolytic enzymes". Thesis, University of Huddersfield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416765.

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Libri sul tema "Enzymes Synthesis"

1

Kirby, Anthony J. From enzyme models to model enzymes. Cambridge: Royal Society of Chemistry, 2009.

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2

Bednarski, Mark D., e Ethan S. Simon, a cura di. Enzymes in Carbohydrate Synthesis. Washington, DC: American Chemical Society, 1991. http://dx.doi.org/10.1021/bk-1991-0466.

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1958-, Bednarski Mark D., Simon Ethan S. 1963-, American Chemical Society. Division of Carbohydrate Chemistry. e American Chemical Society Meeting, a cura di. Enzymes in carbohydrate synthesis. Washington, DC: American Chemical Society, 1991.

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library, Wiley online, a cura di. Asymmetric organic synthesis with enzymes. Weinheim: Wiley-VCH, 2008.

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Holland, H. L. Organic synthesis with oxidative enzymes. New York: VCH, 1992.

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Holland, Herbert L. Organic synthesis with oxidative enzymes. Weinheim: VCH, 1991.

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Wong, Chi-Huey. Enzymes in synthetic organic chemistry. Oxford, U.K: Pergamon, 1994.

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Ronald, Breslow, a cura di. Artificial enzymes. Weinheim: Wiley-VCH, 2005.

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Schneider, M. P., a cura di. Enzymes as Catalysts in Organic Synthesis. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4686-6.

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P, Schneider M., a cura di. Enzymes as catalysts in organic synthesis. Dordrecht, Holland: D. Reidel Pub. Co., 1986.

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Capitoli di libri sul tema "Enzymes Synthesis"

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Ullmann, Dirk, e Hans-Dieter Jakubke. "Protease-Catalyzed Peptide Synthesis". In Proteolytic Enzymes, 312–28. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-642-59816-6_18.

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Aehle, Wolfgang, e Juergen Eck. "Discovery of Enzymes". In Enzyme Catalysis in Organic Synthesis, 67–87. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2012. http://dx.doi.org/10.1002/9783527639861.ch3.

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Roberts, S. M. "Enzymes in Organic Synthesis". In Microbial Enzymes and Biotechnology, 395–424. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0765-2_12.

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Tiwari, Vinod K., Abhijeet Kumar, Sanchayita Rajkhowa, Garima Tripathi e Anil Kumar Singh. "Enzymes in Organic Synthesis". In Green Chemistry, 317–52. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-2734-8_8.

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Pleiss, Jürgen. "Rational Design of Enzymes". In Enzyme Catalysis in Organic Synthesis, 89–117. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2012. http://dx.doi.org/10.1002/9783527639861.ch4.

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Reetz, Manfred T. "Directed Evolution of Enzymes". In Enzyme Catalysis in Organic Synthesis, 119–90. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2012. http://dx.doi.org/10.1002/9783527639861.ch5.

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Bentley, Paul A. "Synthetic Enzymes-Artificial Peptides in Stereoselective Synthesis". In Biotechnology, 491–517. Weinheim, Germany: Wiley-VCH Verlag GmbH, 2008. http://dx.doi.org/10.1002/9783527620913.ch12.

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Turner, N. J. "Asymmetric synthesis using enzymes and whole cells". In Advanced Asymmetric Synthesis, 260–74. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-007-0797-9_13.

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Mosbach, Klaus. "Immobilized Enzymes in Organic Synthesis". In Ciba Foundation Symposium 111 - Enzymes in Organic Synthesis, 57–75. Chichester, UK: John Wiley & Sons, Ltd., 2008. http://dx.doi.org/10.1002/9780470720929.ch6.

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Rozzell, David. "Tabular Survey of Available Enzymes". In Enzyme Catalysis in Organic Synthesis, 1847–938. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2012. http://dx.doi.org/10.1002/9783527639861.ch46.

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Atti di convegni sul tema "Enzymes Synthesis"

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Grebennikova, Olga, Aloeksandrina Sulman e Valentina Matveeva. "SYNTHESIS OF MAGNETICALLY SEPARATED BIOCATALYTIC SYSTEMS". In 22nd SGEM International Multidisciplinary Scientific GeoConference 2022. STEF92 Technology, 2022. http://dx.doi.org/10.5593/sgem2022/6.1/s25.16.

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The use of magnetic nanoparticles in biocatalysis, due to their unique properties, such as controlled particle size, large surface area, and ease of separating them and the reaction mixture by applying an external magnetic field, makes it possible to reuse enzymes immobilized on magnetic nanoparticles for catalytic processes. In this work, horseradish root peroxidase was immobilized on Fe3O4 magnetic nanoparticles. The carrier surface was modified and activated before enzyme immobilization using 3- aminopropyltriethoxysilane and glutaraldehyde. Testing of biocatalytic systems was carried out in the oxidation reaction of 2,2'-azino-bis-(3-ethylbenzthiozolin-6-sulfonic acid) diammonium salt with hydrogen peroxide. The immobilized enzyme showed high efficiency and stability compared to the native enzyme. Also, in the work, the joint immobilization of peroxidase and glucose oxidase on magnetically attached carriers was studied. Enzymes were immobilized on Fe3O4 magnetic nanoparticles and SiO2. Optimal conditions (temperature, pH) were selected for all biocatalytic systems.
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Davis, Benjamin G. "SUGARS AND ENZYMES: PROTEIN GLYCOSYLATION AND GLYCOSIDE SYNTHESIS". In XXIst International Carbohydrate Symposium 2002. TheScientificWorld Ltd, 2002. http://dx.doi.org/10.1100/tsw.2002.411.

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Terwilliger, Thomas C., e Joel Berendzen. "Protein Crystallography: From X-ray diffraction spots to a three-dimensional image". In Signal Recovery and Synthesis. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/srs.1998.swa.1.

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Proteins are remarkable molecular machines that are essential for life. They can do many things ranging from the precise control of blood clotting to synthesizing complex organic compounds. Pictures of protein molecules are in high demand in biotechnology because they are important for applications such as drug discovery and for engineering enzymes for commercial use.
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Bogojevic, Oliver, Carl Arevang e Zheng Guo. "Synthesis of complex phospholipid species". In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/rlyh7861.

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Abstract (sommario):
Phospholipids are essential for the preservation of life on the planet and carry numerous critical roles and functions, including being the main constituents of the cell-membranes in both eukaryotic and prokaryotic cells, providing (more bioavailable) energy, and maintaining chemical and electrical processes in the body. The structural characteristics of phospholipids can vary greatly among species, however, commonly consist of a hydrophilic region (phosphate-containing head-group) and a hydrophobic region (fatty acids, €œtails€), providing the amphiphilic features and unique functions. The countless number of possible configurations enables the continuous synthesis of novel phospholipid species. The synthesis of specific phospholipids, so-called €œdesigner-phospholipids€, is commonly carried out through modifications of more common and easily accessible phospholipid species, catalyzed by the use of either non-specific chemical catalysts or specific enzymes. Enzymatic methods, being most prominent, are often using biphasic reaction systems, allowing for the easy reuse of enzymes and separation of polar compounds, offering more environmentally friendly approaches'. The synthesis of complex phospholipids such as cardiolipins (CLs) and bis(mono/di-acylglycero)phopshates (BMPs/BDPs) have significant value as they carry the unique ability to contain multiple fatty acids, which in turn can be linked to a range of positive health effects. The positive health effects of fish oils (EPA/DHA) are today a hot topic, which in combination with complex phospholipids present great potential for future applications. Additionally, new phospholipid species are continuously under development utilizing completely new synthetic systems with environmentally friendly approaches' in focus. Modern methods centralized on the combinatorial use of ionic liquids and enzymes for the production of novel phospholipids species reduce the use of organic solvents, allowing for the incorporation of fatty acid esters of hydroxy fatty acids (FAHFAs) into phospholipids. The science behind the synthesis of phospholipids is continuously developing for an increased amount of different applications.
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5

Daineko, A. V., A. B. Bulatovski e A. I. Zinchenko. "STUDY ON POTENTIAL ENGINEERING OF ESCHERICHIA COLI XANTHOSE PHOSPHORYLASE STRAIN-PRODUCER". In SAKHAROV READINGS 2021: ENVIRONMENTAL PROBLEMS OF THE XXI CENTURY. International Sakharov Environmental Institute of Belarusian State University, 2021. http://dx.doi.org/10.46646/sakh-2021-2-38-41.

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Genetic engineering is an actively developing branch of modern biotechnology. Using the methods of genetic engineering, it is possible to construct new forms of microorganisms that can synthesize a variety of substances, including enzymes. Xanthosine phosphorylase is the second purine nucleoside phosphorylase (PNP-II) in E. coli. This enzyme performs both reactions of phosphorolysis and the synthesis of purine deoxy / ribonucleosides. Due to this ability, xanthosine phosphorylase can catalyze the reaction of the formation of nicotinamide riboside. This substance is a precursor of the most important coenzyme NAD+ in the body, which plays a key role in the aging process. As a result of the study, a new strain of E. coli pET42a-xapA was constructed. This strain produces the protein xanthosine phosphorylase.
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6

Mazumder, Sonal, Suvojit Ghosh, Joseph O. Falkinham e Ishwar K. Puri. "Factors Affecting the Assembly of Carbon Nanostructures With Cells and Enzymes". In ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology. ASMEDC, 2010. http://dx.doi.org/10.1115/nemb2010-13258.

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Carbon nanostructures were synthesized and deposited through flame synthesis on stainless steel grids and foils, and on bare and ferrofluid-painted silicon wafers at different nonpremixed flame locations to produce hydrophobic surfaces. The hydrophobicity is characterized through the contact angle for water droplets placed on the surface. The surface morphology of the nanoparticles is obtained from high-resolution FESEM images. Following synthesis and deposition the adherence, activity, and stability of bacterial cells, antibodies, and enzymes on the carbon nanostructures can be studied.
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7

Gao, Junshan. "BmPCD and BmDHPR: Two BH4 synthesis enzymes are activated in theBombyx morimutantlem". In 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.110345.

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8

Hassan, Shady S., Gwilym A. Williams e Amit K. Jaiswa. "Fungus-Mediated Synthesis of magnetic nanoparticles for immobilisation of Pectolytic and xylanolytic enzymes". In The 6th World Congress on New Technologies. Avestia Publishing, 2020. http://dx.doi.org/10.11159/icnfa20.134.

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9

Szczepaniak, Sylwia A., Jacek Jemielity, Joanna Zuberek, Joanna Kufel e Edward Darżynkiewicz. "Synthesis of nonhydrolyzable cap analog substituted sepharose for affinity purification of decaping enzymes". In XIVth Symposium on Chemistry of Nucleic Acid Components. Prague: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 2008. http://dx.doi.org/10.1135/css200810461.

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10

Radzi, S. Mat, M. N. Mohd Zulhilmi, H. Mohd Noor e M. Mohd Rehan. "Preliminary study on the synthesis of kojic acid monooleate using dual enzymes system". In GREEN DESIGN AND MANUFACTURE: ADVANCED AND EMERGING APPLICATIONS: Proceedings of the 4th International Conference on Green Design and Manufacture 2018. Author(s), 2018. http://dx.doi.org/10.1063/1.5066873.

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Rapporti di organizzazioni sul tema "Enzymes Synthesis"

1

Granot, David, Scott Holaday e Randy D. Allen. Enhancing Cotton Fiber Elongation and Cellulose Synthesis by Manipulating Fructokinase Activity. United States Department of Agriculture, 2008. http://dx.doi.org/10.32747/2008.7613878.bard.

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Abstract (sommario):
a. Objectives (a) Identification and characterization of the cotton fiber FRKs; (b) Generating transgenic cotton plants overproducing either substrate inhibited tomato FRK or tomato FRK without substrate inhibition; (c) Generating transgenic cotton plants with RNAi suppression of fiber expressed FRKs; (d) Generating Arabidopsis plants that over express FRK1, FRK2, or both genes, as additional means to assess the contribution of FRK to cellulose synthesis and biomass production. b. Background to the topic: Cellulose synthesis and fiber elongation are dependent on sugar metabolism. Previous results suggested that FRKs (fructokinase enzymes that specifically phosphorylate fructose) are major players in sugar metabolism and cellulose synthesis. We therefore hypothesized that increasing fructose phosphorylation may enhance fiber elongation and cellulose synthesis in cotton plants. Accordinlgy, the objectives of this research were: c. Major conclusions and achievements: Two cotton FRKs expressed in fibers, GhFRK2 and GhFRK3, were cloned and characterized. We found that GhFRK2 enzyme is located in the cytosol and GhFRK3 is located within plastids. Both enzymes enable growth on fructose (but not on glucose) of hexose kinase deficient yeast strain, confirming the fructokinase activity of the cloned genes. RNAi constructs with each gene were prepared and sent to the US collaborator to generate cotton plants with RNAi suppression of these genes. To examine the effect of FRKs using Arabidopsis plants we generated transgenic plants expressing either LeFRK1 or LeFRK2 at high level. No visible phenotype has been observed. Yet, plants expressing both genes simultaneously are being created and will be tested. To test our hypothesis that increasing fructose phosphorylation may enhance fiber cellulose synthesis, we generated twenty independent transgenic cotton plant lines overexpressing Lycopersicon (Le) FRK1. Transgene expression was high in leaves and moderate in developing fiber, but enhanced FRK activity in fibers was inconsistent between experiments. Some lines exhibited a 9-11% enhancement of fiber length or strength, but only one line tested had consistent improvement in fiber strength that correlated with elevated FRK activity in the fibers. However, in one experiment, seed cotton mass was improved in all transgenic lines and correlated with enhanced FRK activity in fibers. When greenhouse plants were subjected to severe drought during flowering and boll development, no genotypic differences in fiber quality were noted. Seed cotton mass was improved for two transgenic lines but did not correlate with fiber FRK activity. We conclude that LeFRK1 over-expression in fibers has only a small effect on fiber quality, and any positive effects depend on optimum conditions. The improvement in productivity for greenhouse plants may have been due to better structural development of the water-conducting tissue (xylem) of the stem, since stem diameters were larger for some lines and the activity of FRK in the outer xylem greater than observed for wild-type plants. We are testing this idea and developing other transgenic cotton plants to understand the roles of FRK in fiber and xylem development. We see the potential to develop a cotton plant with improved stem strength and productivity under drought for windy, semi-arid regions where cotton is grown. d. Implications, scientific and agricultural: FRKs are probably bottle neck enzymes for biomass and wood synthesis and their increased expression has the potential to enhance wood and biomass production, not only in cotton plants but also in other feed and energy renewable plants.
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2

Lurie, Susan, John Labavitch, Ruth Ben-Arie e Ken Shackel. Woolliness in Peaches and Nectarines. United States Department of Agriculture, 1995. http://dx.doi.org/10.32747/1995.7570557.bard.

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Abstract (sommario):
The overall goal of the research was to understand the processes involved in the development of woolliness in peaches and nectarines. Four specific hypotheses were proposed and in the course of the research evidence was gathered t support two of them and to not support two others. The hypotheses and a summary of the evidence are outlined below. 1. That woolliness arises from an imbalance between the activities of the cell wall pectin degrading enzymes. Using 'Flavortop' nectarines and 'Hermoza' peaches as model systems, storage regimes were manipulated to induce or prevent woolliness. The expression (mRNA abundance), protein content (Western blotting), and activity of polygalacturonase (PG) and pectin esterase (PE) were followed. Expression of the enzymes was not different, but activity and the ratio between PG and PE activities were quite different in fruits developing woolliness or ripening normally. This was also examined by looking at the substrate, the pectin moiety of the cell wall, and i woolly fruit there were more high molecular weight pectins with regions of non-methylated galacturonic acid residues. Taking an in vitro approach it was found a) that PE activity was stable at 0oC while PG activity decreased; b) incubating the calcium pectate fraction of the cell wall with PE extracted from peaches caused the polymers to form a gel characteristic of the visual woolly symptoms in peaches. 2. That continued cell wall synthesis occurs during storage and contributes to structural changes i cell walls and improper dissolution and softening after storage. We tried to adapt our technique of adding 13C-glucose to fruit discs, which was used successfully to follow cell wall synthesis during tomato ripening. However, the difference in sugar content between the two fruits (4% in tomato and 12% in peach) meant that the 13C-glucose was much more diluted within the general metabolite pool. We were unable to see any cell wall synthesis which meant that either the dilution factor was too great, or that synthesis was not occurring. 3. That controlled atmosphere (CA) prevents woolliness by lowering all enzyme activities. CA was found to greatly reduce mRNA abundance of the cell wall enzymes compared to regular air storage. However, their synthesis and activity recovered during ripening after CA storage and did not after regular air storage. Therefore, CA prevented the inhibition of enzyme activation found in regular air storage. 4. That changes in cell wall turgor and membrane function are important events in the development of woolliness. Using a micro pressure probe, turgor was measured in cells of individual 'O'Henry' and 'CalRed' peaches which were woolly or healthy. The relationship between firmness and turgor was the same in both fruit conditions. These data indicate that the development and expression of woolliness are not associated with differences in membrane function, at least with regard to the factors that determine cell turgor pressure. In addition, during the period of the grant additional areas were explored. Encoglucanase, and enzyme metabolizing hemicellulose, was found to be highly expressed air stored, but not in unstored or CA stored fruit. Activity gels showed higher activity in air stored fruit as well. This is the first indication that other components of the cell wall may be involved in woolliness. The role of ethylene in woolliness development was also investigated at it was found a) that woolly fruits had decreased ability to produce ethylene, b) storing fruits in the presence of ethylene delayed the appearance of woolliness. This latter finding has implication for an inexpensive strategy for storing peaches and nectarines.
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3

Prusky, Dov, Noel Keen e Rolf Christoffersen. Involvement of Epicatechin in the Regulation of Natural Resistance of Avocado Fruit against Postharvest Pathogens. United States Department of Agriculture, gennaio 1997. http://dx.doi.org/10.32747/1997.7613028.bard.

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In this project it was found that the activation of the mechanism of resistance in avocado fruits to Colletotrichum gloeosporioides depends on the increase of the level of the preformed antifungal diene. This increase is regulated by the synthesis of the flavonoid epicatechin present in the fruit peel. Epicatechin is an inhibitor of the enzyme lipoxygenase whose activity catalyze the breakdown of the antifungal diene. Increase in epicatechin concentration inhibits the breakdown of the antifungal compound and since the compound is continuously synthesized, both combined processes result in the increase of the antifungal level. Biotic and abiotic elicitors affecting the mechanism of resistance, all activate the synthesis of epicatechin. As abiotic elicitors were tested wounding, ethylene and CO2 treatments. As biotic elicitors were tested challenge inoculation with C. gloeosporioides, Colletotrichum magna (a non pathogen of avocado) and also non pathogenic strain of C. magna. In all the cases activation of the key enzymes of the phenylpropanoic pathway is followed by an enhance in the level of epicatechin and the antifungal diene. In order to determine the level of regulation by the different elicitors of the mechanism, the genes encoding for key enzymes of the phenylpropanoic pathway were cloned and it was found that the different elicitors regulate the expression of those genes at a translational level. Modulation of the mechanism of resistance could also be done by activation of lipoxygenase gene expression. For this purpose lipoxygenase from avocado was cloned and its over-expression, under the effect of methyl jasmonate, determined.
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4

Amir, Rachel, David J. Oliver, Gad Galili e Jacline V. Shanks. The Role of Cysteine Partitioning into Glutathione and Methionine Synthesis During Normal and Stress Conditions. United States Department of Agriculture, gennaio 2013. http://dx.doi.org/10.32747/2013.7699850.bard.

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Abstract (sommario):
The objective of this research is to study the nature of the competition for cysteine (Cys), the first organic sulfur-containing compound, between its two main metabolites, glutathione (GSH) and methionine (Met). GSH plays a central role in protecting plants during various stresses, while Met, an essential amino acid, regulates essential processes and metabolites in plant cells through its metabolite S-adenosyl-Met. Our results, which are based on flux analysis and measurements of Met- metabolites, show that the flux towards Met synthesis is high during non-stress conditions, however the flux is significantly reduced under stress conditions, when there is high synthesis of GSH. Under oxidative stress the expression level of the regulatory enzyme of Met synthesis, cystathionine g-synthase (CGS) was reduced. By using three different systems, we have found that that GSH down regulates the expression level of CGS, thus reducing Met synthesis. We have found that this regulation occurs at the post-transcriptional level, and further studies have shown that it occurs at post-translationaly. To reveal how oxidative stress affects the flux towards Met and GSH, flux analysis was performed. We have found that the level of Met is significantly reduced, while the level of glutathione significantly increases during stress. Under stress conditions most of the glutathione is converted from GSH to GSSG (the oxidised form of glutathione). These results suggest that under normal growth conditions, Cys is channelled towards both pathways to support GSH accumulation and the synthesis of growth-essential Met metabolites. However, during oxidative stress, when a high level of GSH is required to protect the plants, the levels of GSH increase while those of CGS are reduced. This reduction leaves more Cys available for GSH synthesis under stress conditions. In addition we have also studied the effects of high GSH level on the transcriptome profile. The analysis revealed that GSH affects the expression level of many major genes coding to enzymes or proteins associated with photosynthesis, starch degradation, hormone metabolism (especially genes associated with jasmonate), biotic stress (especially genes associated with PR-proteins), cytochrome P450 genes, regulation of transcription and signaling (especially genes associated with receptor kinases and calcium). These results suggest that indeed GSH levels affect different pathways and metabolites in plants.
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5

Sukenik, Assaf, Paul Roessler e John Ohlrogge. Biochemical and Physiological Regulation of Lipid Synthesis in Unicellular Algae with Special Emphasis on W-3 Very Long Chain Lipids. United States Department of Agriculture, gennaio 1995. http://dx.doi.org/10.32747/1995.7604932.bard.

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Abstract (sommario):
Various unicellular algae produce omega-3 (w3) very-long-chain polyunsaturated fatty acids (VLC-PUFA), which are rarely found in higher plants. In this research and other studies from our laboratories, it has been demonstrated that the marine unicellular alga Nannochloropsis (Eustigmatophyceae) can be used as a reliable and high quality source for the w3 VLC-PUFA eicosapentaenoic acid (EPA). This alga is widely used in mariculture systems as the primary component of the artificial food chain in fish larvae production, mainly due to its high EPA content. Furthermore, w3 fatty acids are essential for humans as dietary supplements and may have therapeutic benefits. The goal of this research proposal was to understand the physiological and biochemical mechanisms which regulate the synthesis and accumulation of glycerolipids enriched with w3 VLC-PUFA in Nannochloropsis. The results of our studies demonstrate various aspects of lipid synthesis and its regulation in the alga: 1. Variations in lipid class composition imposed by various environmental conditions were determined with special emphasis on the relative abundance of the molecular species of triacylglycerol (TAG) and monogalactosyl diacylglycerol (MGDG). 2. The relationships between the cellular content of major glycerolipids (TAG and MGDG) and the enzymes involved in their synthesis were studied. The results suggested the importance of UDP-galactose diacylglycerol galactosyl (UDGT) in regulation of the cellular level of MGDG. In a current effort we have purified UDGT several hundredfold from Nannochloropsis. It is our aim to purify this enzyme to near homogeneity and to produce antibodies against this enzyme in order to provide the tools for elucidation of the biochemical mechanisms that regulate this enzyme and carbon allocation into galactolipids. 3. Our in vitro and in vivo labeling studies indicated the possibility that phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are associated with desaturation of the structural lipids, whereas shorter chain saturated fatty acids are more likely to be incorporated into TAG. 4. Isolation of several putative mutants of Nannochloropsis which appear to have different lipid and fatty acid compositions than the wild type; a mutant of a special importance that is devoid of EPA was fully characterized. In addition, we could demonstrate the feasibility of Nannochloropsis biomass production for aquaculture and human health: 1) We demonstrated in semi-industrial scale the feasibility of mass production of Nannochloropsis biomass in collaboration with the algae plant NBT in Eilat; 2) Nutritional studies verified the importance algal w3 fatty acids for the development of rats and demonstrated that Nannochloropsis biomass fed to pregnant and lactating rats can benefit their offspring.
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6

Sharon, Amir, e Maor Bar-Peled. Identification of new glycan metabolic pathways in the fungal pathogen Botrytis cinerea and their role in fungus-plant interactions. United States Department of Agriculture, 2012. http://dx.doi.org/10.32747/2012.7597916.bard.

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Abstract (sommario):
The involvement of glycans in microbial adherence, recognition and signaling is often a critical determinant of pathogenesis. Although the major glycan components of fungal cell walls have been identified there is limited information available on its ‘minor sugar components’ and how these change during different stages of fungal development. Our aim was to define the role of Rhacontaining-glycans in the gray mold disease caused by the necrotrophic fungus B. cinerea. The research was built on the discovery of two genes, Bcdhand bcer, that are involved in formation of UDP-KDG and UDP-Rha, two UDP- sugars that may serve as donors for the synthesis of cell surface glycans. Objectives of the proposed research included: 1) To determine the function of B. cinereaBcDh and BcEr in glycan biosynthesis and in pathogenesis, 2) To determine the expression pattern of BcDH and BcERand cellular localization of their encoded proteins, 3) Characterize the structure and distribution of Rha- containing glycans, 4) Characterization of the UDP-sugar enzymes and potential of GTs involved in glycanrhamnosylation. To address these objectives we generated a series of B. cinereamutants with modifications in the bchdhand bcergenes and the phenotype and sugar metabolism in the resulting strains were characterized. Analysis of sugar metabolites showed that changes in the genes caused changes in primary and secondary sugars, including abolishment of rhamnose, however abolishment of rhamnose synthesis did not cause changes in the fungal phenotype. In contrast, we found that deletion of the second gene, bcer, leads to accumulation of the intermediate sugar – UDP- KDG, and that such mutants suffer from a range of defects including reduced virulence. Further analyses confirmed that UDP-KDG is toxic to the fungus. Studies on mode of action suggested that UDP-KDG might affect integrity of the fungal cell wall, possibly by inhibiting UDP-sugars metabolic enzymes. Our results confirm that bcdhand bcerrepresent a single pathway of rhamnose synthesis in B. cinerea, that rhamnose does not affect in vitro development or virulence of the fungus. We also concluded that UDP-KDG is toxic to B. cinereaand hence UDP-KDG or compounds that inhibit Er enzymes and lead to accumulation of UDP-KDG might have antifungal activity. This toxicity is likely the case with other fungi, this became apparent in a collaborative work with Prof. Bart Thomma of Wageningen University, NETHERLANDS . We have shown the deletion of ER mutant in Verticillium dahlia gave plants resistance to the fungal infection.
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7

Stewart, John M., Karl Hahn e Wieslaw A. Klis. Synthetic Helizyme Enzymes. Fort Belvoir, VA: Defense Technical Information Center, agosto 1989. http://dx.doi.org/10.21236/ada211789.

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8

Manulis, Shulamit, Christine D. Smart, Isaac Barash, Guido Sessa e Harvey C. Hoch. Molecular Interactions of Clavibacter michiganensis subsp. michiganensis with Tomato. United States Department of Agriculture, gennaio 2011. http://dx.doi.org/10.32747/2011.7697113.bard.

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Abstract (sommario):
Clavibacter michiganensis subsp. michiganensis (Cmm), the causal agent of bacterial wilt and canker of tomato, is the most destructive bacterial disease of tomato causing substantial economic losses in Israel, the U.S.A. and worldwide. The molecular strategies that allow Cmm, a Gram-positive bacterium, to develop a successful infection in tomato plants are largely unknown. The goal of the project was to elucidate the molecular interactions between Cmmand tomato. The first objective was to analyze gene expression profiles of susceptible tomato plants infected with pathogenic and endophytic Cmmstrains. Microarray analysis identified 122 genes that were differentially expressed during early stages of infection. Cmm activated typical basal defense responses in the host including induction of defense-related genes, production of scavenging of free oxygen radicals, enhanced protein turnover and hormone synthesis. Proteomic investigation of the Cmm-tomato interaction was performed with Multi-Dimensional Protein Identification Technology (MudPIT) and mass spectroscopy. A wide range of enzymes secreted by Cmm382, including cell-wall degrading enzymes and a large group of serine proteases from different families were identified in the xylem sap of infected tomato. Based on proteomic results, the expression pattern of selected bacterial virulence genes and plant defense genes were examined by qRT-PCR. Expression of the plasmid-borne cellulase (celA), serine protease (pat-1) and serine proteases residing on the chp/tomA pathogenicity island (chpCandppaA), were significantly induced within 96 hr after inoculation. Transcription of chromosomal genes involved in cell wall degradation (i.e., pelA1, celB, xysA and xysB) was also induced in early infection stages. The second objective was to identify by VIGS technology host genes affecting Cmm multiplication and appearance of disease symptoms in plant. VIGS screening showed that out of 160 tomato genes, which could be involved in defense-related signaling, suppression of 14 genes led to increase host susceptibility. Noteworthy are the genes Snakin-2 (inhibitor of Cmm growth) and extensin-like protein (ELP) involved in cell wall fortification. To further test the significance of Snakin -2 and ELP in resistance towards Cmm, transgenic tomato plants over-expressing the two genes were generated. These plants showed partial resistance to Cmm resulting in a significant delay of the wilt symptoms and reduction in size of canker lesion compared to control. Furthermore, colonization of the transgenic plants was significantly lower. The third objective was to assess the involvement of ethylene (ET), jasmonate (JA) and salicylic acid (SA) in Cmm infection. Microarray and proteomic studies showed the induction of enzymes involved in ET and JA biosynthesis. Cmm promoted ET production 8 days after inoculation and SIACO, a key enzyme of ET biosynthesis, was upregulated. Inoculation of the tomato mutants Never ripe (Nr) impaired in ET perception and transgenic plants with reduced ET synthesis significantly delayed wilt symptoms as compared to the wild-type plants. The retarded wilting in Nr plants was shown to be a specific effect of ET insensitivity and was not due to altered expression of defense related genes, reduced bacterial population or decrease in ethylene biosynthesis . In contrast, infection of various tomato mutants impaired in JA biosynthesis (e.g., def1, acx1) and JA insensitive mutant (jai1) yielded unequivocal results. The fourth objective was to determine the role of cell wall degrading enzymes produced by Cmm in xylem colonization and symptoms development. A significance increase (2 to 7 fold) in expression of cellulases (CelA, CelB), pectate lyases (PelA1, PelA2), polygalacturonase and xylanases (XylA, XylB) was detected by qRT-PCR and by proteomic analysis of the xylem sap. However, with the exception of CelA, whose inactivation led to reduced wilt symptoms, inactivation of any of the other cell wall degrading enzymes did not lead to reduced virulence. Results achieved emphasized the complexity involved in Cmm-tomato interactions. Nevertheless they provide the basis for additional research which will unravel the mechanism of Cmm pathogenicity and formulating disease control measures.
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Nicholson, Ralph, Reuven Reuveni e Moshe Shimoni. Biochemical Markers for Disease Resistance in Corn. United States Department of Agriculture, maggio 1996. http://dx.doi.org/10.32747/1996.7613037.bard.

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Abstract (sommario):
The objective was to screen maize lines for their ability to express resistance based on biochemical traits. Cultivars were screened for retention of the hydroxamic acid DIMBOA and the synthesis of phenols (based on anthocyanin production) as markers for resistance. Lines were selected and inoculated with fungal pathogens (Exserohilum turcicum, Puccinia sorghi, Cochliobolus heterostraphus, Colletotricum graminicola.), and the Maize Dwarf Mosaic and Johnson Grass Mosaic viruses. Lines were screened in the field and greenhouse. Results showed that lines selected for augmented phenol synthesis do exhibit heightened levels of resistance to fungal pathogens. Isolation of mRNA followed by northern analyses for expression of A1 (dihydroflavanol reductase) and peroxidase confirmed that genes for these enzymes were turned on in response to inoculation of lines predicted to exhibit resistance. Peroxidase and b-1,3-glucanase were assayed in breeding lines having or lacking the se gene. A specific ionically-bound peroxidase isozyme and a b-1,3-glucanase isozyme were revealed in lines having the se gene. Data suggest that peroxidase and b-1,3-glucanase isozymes, may be considered as markers to identify resistance to E. turcicum in maize genotypes with the se gene.
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10

Gantt, Elisabeth, Avigad Vonshak, Sammy Boussiba, Zvi Cohen e Amos Richmond. Carotenoid-Rich Algal Biomass for Aquaculture: Astaxanthin Production by Haematococcus Pluvialis. United States Department of Agriculture, agosto 1996. http://dx.doi.org/10.32747/1996.7613036.bard.

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Abstract (sommario):
The synthesis of carotenoids has been studied toward enhancing the production of ketocarotenoids, since fish and crustaceans raised by aquaculture require astaxanthin and other ketocaroteinoids in their feed for desirable pigmentation. Notable progress has been made in attaining the goals of determining improved conditions for ketocarotenoid production in Haematococcus pluvialis and in elucidating the carotenoid biosynthetic pathway. For production of astaxanthin a number of strains of the green alga Haematococcus were evaluated, a strain CCAG was found to be optimal for photoautotrophic growth. Of four mutants, selected for enhanced carotenoid production, two hold considerable promise because caroteinoid accumulation occurs without encystment. The biosynthetic pathway of carotenoids was elucidated in photosynthetic organisms by characterizing novel genes encoding carotenoid enzymes and by examining the function of these enzymes in a bacterial complementation system. Two cyclases (b- and e-) were cloned that are at a critical branch point in the pathway. One branch leads to the formation of b-carotene and zeaxanthin and astaxanthin, and the other to the production of a-carotene and lutein. Cyclization of both endgroups of lycopene to yield b-carotene was shown to be catalyzed by a single gene product, b-lycopene cyclase in cyanobacteria and plants. The formation of a-carotene was found to require the e-cyclase gene product in addition to the b-cyclase. By cloning a b-hydroxylase gene we showed that a single gene product forms zeaxanthin by hydroxylatin of both b-carotene rings. It is expected that a second hydroxylase is required in the synthesis of astaxanthin, since canthaxanthin rather than zeaxanthin is the precursor. Evidence, from inhibitor studies, suggests that astaxanthin is formed from canthaxanthin and that b-carotene is a major precursor. Feasibility studies with the photobioreactors have shown that a two-stage system is the most practical, where Haematococcus cultures are first grown to high cell density and are then switched to high light for maximal astaxanthin production. The basic knowledge and molecular tools generated from this study will significantly enhance Haematococcus as a viable model for enhanced astaxanthin production.
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