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Enzymatic Process (enzymatic + process)
Selected AbstractsA Feasible Enzymatic Process for d -Tagatose Production by an Immobilized Thermostable l -Arabinose Isomerase in a Packed-Bed BioreactorBIOTECHNOLOGY PROGRESS, Issue 2 2003Hye-Jung Kim To develop a feasible enzymatic process for d -tagatose production, a thermostable l -arabinose isomerase, Gali152, was immobilized in alginate, and the galactose isomerization reaction conditions were optimized. The pH and temperature for the maximal galactose isomerization reaction were pH 8.0 and 65 °C in the immobilized enzyme system and pH 7.5 and 60 °C in the free enzyme system. The presence of manganese ion enhanced galactose isomerization to tagatose in both the free and immobilized enzyme systems. The immobilized enzyme was more stable than the free enzyme at the same pH and temperature. Under stable conditions of pH 8.0 and 60 °C, the immobilized enzyme produced 58 g/L of tagatose from 100 g/L galactose in 90 h by batch reaction, whereas the free enzyme produced 37 g/L tagatose due to its lower stability. A packed-bed bioreactor with immobilized Gali152 in alginate beads produced 50 g/L tagatose from 100 g/L galactose in 168 h, with a productivity of 13.3 (g of tagatose)/(L-reactor·h) in continuous mode. The bioreactor produced 230 g/L tagatose from 500 g/L galactose in continuous recycling mode, with a productivity of 9.6 g/(L·h) and a conversion yield of 46%. [source] Facile Synthesis of Enantiopure 4-Substituted 2-Hydroxy-4- butyrolactones using a Robust Fusarium LactonaseADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Bing Chen Abstract A facile chemo-enzymatic process has been developed for producing stereoisomers of 4-substituted 2-hydroxy-4-butyrolactones with good to excellent enantioselectivity. This process involves an easy separation of the diastereoisomers by column chromatography and efficient enzymatic resolution by whole cells of Escherichia coli JM109 expressing Fusarium proliferatum lactonase gene. This biocatalyst shows strong tolerance towards different substrate structures and at least three out four possible isomers could be obtained in excellent enantiomeric purity. Different substrate concentrations (10,mM,200,mM) were examined, giving a substrate to catalyst ratio of up to 26:1. This general and efficient enzymatic process provides access to stereoisomers of 4-substituted 2-hydroxy-4-butyrolactones readily and cost-effectively. The stereochemical assignments were conducted systematically based on NMR, X-ray diffraction and circular dichroism, leading to further understanding of the enzyme's stereoselectivity. [source] One-Pot Conversion of Cephalosporin C to 7-Aminocephalosporanic Acid in the Absence of Hydrogen PeroxideADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14 2005Fernando Lopez-Gallego Abstract The main drawback in the production of 7-aminocephalosporanic acid (7-ACA) at the industrial level is the inactivation of the enzymes implicated in the process due to the presence of hydrogen peroxide during the reaction. As an alternative, we have developed the conversion of cephalosporin C to 7-ACA in a single reactor without the presence of hydrogen peroxide during the reaction, achieving more than 80% yield. In order to develop this process, D -amino acid oxidase (DAAO) was co-immobilized with catalase (CAT), which is able to fully eliminate in situ the hydrogen peroxide formed by the neighbouring DAAO molecules. Thus, the product of the reaction is only ,-ketoadipyl-7-ACA. This system prevents the inactivation of the oxidase by hydrogen peroxide, solving the main problem of the enzymatic process. Moreover, we have found that ,-ketoadipyl-7-ACA is recognized as a substrate by glutaryl acylase (GAC) and hydrolyzed as long as glutaric acid is absent from the reaction medium (because it is able to inhibit the hydrolysis). The low stability of ,-ketoadipyl-7-ACA justifies the use of a single reactor, in which glutaryl acylase is already present when this substrate is generated. Thus, the whole process may (and must) be performed in a single step, and in the absence of hydrogen peroxide that could affect the stabilities of the involved enzymes. [source] Enantioselective Enzymatic Cleavage of N -Benzyloxycarbonyl GroupsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6-7 2003Ramesh Abstract A new enzymatic process for the enantioselective cleavage of N -benzyloxycarbonyl (Cbz) groups from protected amino acids and related compounds has been developed. The Cbz-deprotecting enzyme was isolated from cell extracts of Sphingomonas paucimobilis SC 16113 and purified to homogeneity. The purified protein has a molecular weight of 155,000 daltons and a subunit size of 44,000 daltons. [source] Structure-based prediction of modifications in glutarylamidase to allow single-step enzymatic production of 7-aminocephalosporanic acid from cephalosporin CPROTEIN SCIENCE, Issue 1 2002Karin Fritz-Wolf Abstract Glutarylamidase is an important enzyme employed in the commercial production of 7-aminocephalosporanic acid, a starting compound in the synthesis of cephalosporin antibiotics. 7-aminocephalosporanic acid is obtained from cephalosporin C, a natural antibiotic, either chemically or by a two-step enzymatic process utilizing the enzymes D-amino acid oxidase and glutarylamidase. We have investigated possibilities for redesigning glutarylamidase for the production of 7-aminocephalosporanic acid from cephalosporin C in a single enzymatic step. These studies are based on the structures of glutarylamidase, which we have solved with bound phosphate and ethylene glycol to 2.5 Å resolution and with bound glycerol to 2.4 Å. The phosphate binds near the catalytic serine in a way that mimics the hemiacetal that develops during catalysis, while the glycerol occupies the side-chain binding pocket. Our structures show that the enzyme is not only structurally similar to penicillin G acylase but also employs essentially the same mechanism in which the ,-amino group of the catalytic serine acts as a base. A subtle difference is the presence of two catalytic dyads, His B23/Glu B455 and His B23/Ser B1, that are not seen in penicillin G acylase. In contrast to classical serine proteases, the central histidine of these dyads interacts indirectly with the O, through a hydrogen bond relay network involving the ,-amino group of the serine and a bound water molecule. A plausible model of the enzyme,substrate complex is proposed that leads to the prediction of mutants of glutarylamidase that should enable the enzyme to deacylate cephalosporin C into 7-aminocephalosporanic acid. [source] Review: Biological methylation of less-studied elementsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2002John S. Thayer Abstract Biological methylation is an enzymatic process in which a methyl group is transferred from one atom to another. For elements having atomic number greater than 11, biological methylation has been most extensively studied for three elements: arsenic, mercury and sulfur. However, many other elements also undergo biological methylation but have received less attention. Recent work on these less-studied elements and new applications of biological methylation to environmental remediation, along with a description of these reactions in terms of bonding models, is the focus of this review. Copyright © 2002 John Wiley & Sons, Ltd. [source] Structure of aminopeptidase N from Escherichia coli complexed with the transition-state analogue aminophosphinic inhibitor PL250ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2009Marie-Claude Fournié-Zaluski Aminopeptidase N (APN; EC 3.4.11.2) purified from Escherichia coli has been crystallized with the optically pure aminophosphinic inhibitor PL250, H3N+ -CH(CH3)-P(O)(OH)-CH2 -CH(CH2Ph)-CONH-CH(CH2Ph)CO2,, which mimics the transition state of the hydrolysis reaction. PL250 inhibits APN with a Ki of 1.5,2.2,nM and its three-dimensional structure in complex with E. coli APN showed its interaction with the S1, S,1 and S,2 subsites of the catalytic site. In this structure, the Zn ion was shown to be pentacoordinated by His297, His301 and Glu320 of APN and the two O atoms of the phosphinic moiety of PL250. One of these O atoms is also involved in a hydrogen bond to Tyr381, supporting the proposed role of this amino acid in the stabilization of the transition state of the enzymatic process. The strength of the phosphinic zinc binding and the occupancy of the S,2 subsite account for the 100-fold increase in affinity of PL250 compared with the dipeptide-derived inhibitor bestatin (Ki = 4.1 × 10,6,M). Accordingly, the removal of the C-terminal phenylalanine of PL250 resulted in a large decrease in affinity (Ki = 2.17 × 10,7,M). Furthermore, it was observed that the C-terminal carboxyl group of the inhibitor makes no direct interactions with the amino acids of the APN active site. Interestingly, PL250 exhibits the same inhibitory potency for E. coli APN and for mammalian enzymes, suggesting that the structure of the complex could be used as a template for the rational design of various human APN inhibitors needed to study the role of this aminopeptidase in various pathologies. [source] A Feasible Enzymatic Process for d -Tagatose Production by an Immobilized Thermostable l -Arabinose Isomerase in a Packed-Bed BioreactorBIOTECHNOLOGY PROGRESS, Issue 2 2003Hye-Jung Kim To develop a feasible enzymatic process for d -tagatose production, a thermostable l -arabinose isomerase, Gali152, was immobilized in alginate, and the galactose isomerization reaction conditions were optimized. The pH and temperature for the maximal galactose isomerization reaction were pH 8.0 and 65 °C in the immobilized enzyme system and pH 7.5 and 60 °C in the free enzyme system. The presence of manganese ion enhanced galactose isomerization to tagatose in both the free and immobilized enzyme systems. The immobilized enzyme was more stable than the free enzyme at the same pH and temperature. Under stable conditions of pH 8.0 and 60 °C, the immobilized enzyme produced 58 g/L of tagatose from 100 g/L galactose in 90 h by batch reaction, whereas the free enzyme produced 37 g/L tagatose due to its lower stability. A packed-bed bioreactor with immobilized Gali152 in alginate beads produced 50 g/L tagatose from 100 g/L galactose in 168 h, with a productivity of 13.3 (g of tagatose)/(L-reactor·h) in continuous mode. The bioreactor produced 230 g/L tagatose from 500 g/L galactose in continuous recycling mode, with a productivity of 9.6 g/(L·h) and a conversion yield of 46%. [source] How microbes utilize host ubiquitinationCELLULAR MICROBIOLOGY, Issue 10 2009Thomas Spallek Summary Activity, abundance and localization of eukaryotic proteins can be regulated through covalent attachment of ubiquitin and ubiquitin-like moieties. Ubiquitination is important in various aspects of immunity. Pathogens utilize host ubiquitination for the suppression of immune signalling and reprogramming host processes to promote microbial life. They deliver so-called effector molecules into host cells, which functionally or structurally resemble components of the host ubiquitination machinery utilizing this enzymatic process or they secrete molecules to inhibit ubiquitin-mediated degradation. Since prokaryotic pathogens lack a classical ubiquitination system, effector mimicry of components of the ubiquitin machinery could be achieved through gene flow. Horizontal gene transfer allows pathogenic bacteria to access ubiquitination enzymes from a potential host, while lateral gene transfer recruits components from another pathogen providing spread within the microbial community. Additionally, convergent evolution can shape bacterial proteins to acquire ubiquitination functions. [source] Overview of retinoid metabolism and functionDEVELOPMENTAL NEUROBIOLOGY, Issue 7 2006Rune Blomhoff Abstract Retinoids (vitamin A) are crucial for most forms of life. In chordates, they have important roles in the developing nervous system and notochord and many other embryonic structures, as well as in maintenance of epithelial surfaces, immune competence, and reproduction. The ability of all- trans retinoic acid to regulate expression of several hundred genes through binding to nuclear transcription factors is believed to mediate most of these functions. The role of all- trans retinoic may extend beyond the regulation of gene transcription because a large number of noncoding RNAs also are regulated by retinoic acid. Additionally, extra-nuclear mechanisms of action of retinoids are also being identified. In organisms ranging from prokaryotes to humans, retinal is covalently linked to G protein-coupled transmembrane receptors called opsins. These receptors function as light-driven ion pumps, mediators of phototaxis, or photosensory pigments. In vertebrates phototransduction is initiated by a photochemical reaction where opsin-bound 11- cis -retinal is isomerized to all- trans -retinal. The photosensitive receptor is restored via the retinoid visual cycle. Multiple genes encoding components of this cycle have been identified and linked to many human retinal diseases. Central aspects of vitamin A absorption, enzymatic oxidation of all- trans retinol to all- trans retinal and all- trans retinoic acid, and esterification of all- trans retinol have been clarified. Furthermore, specific binding proteins are involved in several of these enzymatic processes as well as in delivery of all- trans retinoic acid to nuclear receptors. Thus, substantial progress has been made in our understanding of retinoid metabolism and function. This insight has improved our view of retinoids as critical molecules in vision, normal embryonic development, and in control of cellular growth, differentiation, and death throughout life. © 2006 Wiley Periodicals, Inc. J Neurobiol 66: 606,630, 2006 [source] Vinyl sulfones: Synthetic preparations and medicinal chemistry applicationsMEDICINAL RESEARCH REVIEWS, Issue 6 2006D. Christopher Meadows Abstract Vinyl sulfones have long been known for their synthetic utility in organic chemistry, easily participating in 1,4-addition reactions and cycloaddition reactions. This functional group has also recently been shown to potently inhibit a variety of enzymatic processes providing unique properties for drug design and medicinal chemistry. This review includes traditional methods used for the synthesis of vinyl sulfones, but focuses mainly on newer reactions applied to vinyl sulfones, including olefin metathesis, conjugate reduction, asymmetric dihydroxylation (AD), and the use of vinyl sulfones to arrive at highly functionalized targets, all illustrating the rich and versatile chemistry this group can efficiently perform. In addition, geminal disulfones are discussed with respect to their formation, reactions, and medicinal applications of this underutilized functional group. © 2006 Wiley Periodicals, Inc. Med Res Rev [source] A mass spectrometry-based strategy for detecting and characterizing endogenous proteinase activities in complex biological samplesPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 3 2008Sarah Robinson Abstract Endogenous proteinases in biological fluids such as human saliva produce a rich peptide repertoire that reflects a unique combination of enzymes, substrates, and inhibitors/activators. Accordingly, this subproteome is an interesting source of biomarkers for disease processes that either directly or indirectly involve proteolysis. However, the relevant proteinases, typically very low abundance molecules, are difficult to classify and identify. We hypothesized that a sensitive technique for monitoring accumulated peptide products in an unbiased, global manner would be very useful for detecting and profiling proteolytic activities in complex biological samples. Building on the longstanding use of 18O isotope-based approaches for the classification of proteolytic and other enzymatic processes we devised a new method for evaluating endogenous proteinases. Specifically, we showed that upon ex vivo incubation endogenous proteinases in human parotid saliva introduced 18O from isotopically enriched water into the C-terminal carboxylic groups of their peptide products. Subsequent peptide sequence determination and inhibitor profiling enabled the detection of discrete subsets of proteolytic products that were generated by different enzymes. As a proof-of-principle we used one of these fingerprints to identify the relevant activity as tissue kallikrein. We termed this technique PALeO. Our results suggest that PALeO is a rapid and highly sensitive method for globally assessing proteinase activities in complex biological samples. [source] Poplar as a feedstock for biofuels: A review of compositional characteristicsBIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 2 2010Poulomi Sannigrahi Abstract The growing demand for transportation fuels, along with concerns about the harmful effects of greenhouse gas emissions from the burning of fossil fuels, has assured a viable future for the development of alternative fuels from renewable resources, such as lignocellulosic biomass. The efficient utilization of these biomass resources is critically dependant on the in-depth knowledge of their chemical constituents. This, together with the desired fuel properties, helps tailor the chemical and/or enzymatic processes involved in converting biomass to biofuels. Hybrid poplars are among the fastest growing temperate trees in the world and a very promising feedstock for biofuels and other value-added products. Sequencing of the poplar genome has paved the way for tailoring new cultivars and clones optimized for biofuels production. Our objective is to review published research on the composition of the key chemical constituents of hybrid poplar species used for biofuels. Biomass yields, elemental composition, carbohydrate and lignin content and composition are some of the characteristics reviewed, with emphasis on lignin structure. Genetic modifications used to alter lignin content and composition, with the aim of improving biofuels yields, are also examined. Copyright © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd [source] Production of biodiesel: possibilities and challengesBIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 1 2007Sulaiman Al-Zuhair Abstract Biodiesel, defined as monoalkyl fatty acid ester (preferentially methyl and ethyl esters), represents a promising alternative fuel for use in compression-ignition (diesel) engines. Biodiesel fuel comes from renewable sources as it is plant- not petroleum-derived and as such it is biodegradable and less toxic. In addition, relative to conventional diesel, its combustion products have reduced levels of particulates, carbon oxides, sulphur oxides and, under some conditions, nitrogen oxides. Enzymatic production of biodiesel has been proposed to overcome the drawbacks of the conventional chemically catalyzed processes. The main obstacle facing full exploitation of the enzyme, lipase, potential is its cost. Therefore, reuse of lipase is essential from the economic point of view, which can be achieved by using the lipase in immobilized form. In addition, immobilized lipase displays improved stability and activity. Common immobilization techniques include attachment to solid supports and entrapment within the matrix of a polymer. This article presents a comparison between conventional processes and enzymatic processes and different possible feedstocks for biodiesel production. In addition, possible ways to overcome the problems facing the use of lipase are described. © 2007 Society of Chemical Industry and John Wiley & Sons, Ltd [source] | |||||||||||||