Enzyme structure and function

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  • Enzymes are proteins that catalyze chemical reactions. A protein is simply a polypeptide composed of amino acids linked by a peptide bond, and the term generally, but not always, refers to the folded conformation. To understand how an enzyme functions, including its binding and functional properties, it is necessary to know the properties of the amino acids and how the amino acids are linked together, including the torsion angles of the bonds and the space occupied, and the interactions of the atoms leading to the final conformations of the folded protein.

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  • The book is intended to provide a sound basis for enzyme reactor design based on kinetic principles, and give an updated vision of the potentials and limitations of enzyme biocatalysis, especially with respect to recent applications in processes of organic synthesis. The book is structured in the form of a textbook that goes from basic principles of enzyme structure and function to reactor design for homogeneous systems with soluble enzymes, and heterogeneous systems with insolubilized enzymes.

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  • Living processes consists almost entirely of biochemical reactions. Without catalysts these reactions would not occur fast enough to sustain life.How does an enzyme do this? ------ because enzyme is a catalytic protein-a chemical agent that changes the rate of a reaction without being consumed by the reaction

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  • Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Minireview cung cấp cho các bạn kiến thức về ngành y đề tài: Influence of metabolic network structure and function on enzyme evolution...

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  • A novel plant protein isolated from the underground bulbs of Scadoxus multiflorus, xylanase and a-amylase inhibitor protein (XAIP), inhibits two structurally and functionally unrelated enzymes: xylanase and a-amylase. The mature protein contains 272 amino acid residues which show sequence identities of 48% to the plant chitinase hevamine and 36% to xylanase inhibitor protein-I, a double-headed inhibitor of GH10 and GH11 xylanases.

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  • Bacterial l-asparaginases are enzymes that catalyze the hydrolysis of l-asparagine to aspartic acid. For the past 30 years, these enzymes have been used as therapeutic agents in the treatment of acute childhood lymphoblastic leukemia.

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  • Cholesterol oxidase is a bacterial FAD-containing flavooxidase that catalyzes the first reaction in cholesterol catabolism. Indeed, this enzyme catalyzes two reactions: the oxidation of the C3 -OH group of cholesterol (and other sterols) to give cholest-5-en-3-one; and its isomerization to cholest-4-en-3-one. In the past several years, the structural and functional characterization of choles-terol oxidase has been developed together with its application as a biological tool.

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  • The structure of the Mg 2+ -dependent enzyme human phosphoserine phosphatase (HPSP) was exploited to examine the structural and functional role of the divalent cation in the active site of phosphatases. Most interesting is the biochemical observation that a Ca 2+ ion inhibits the activity of HPSP, even in the presence of added Mg 2+ .The sixfold coordinated Mg 2+ ion present in the active site of HPSP under normal physiological conditions, was replaced by a Ca 2+ ion by using a crystallization conditionwith high concentration of CaCl2(0.7M). ...

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  • Although belonging to the widely investigated peroxidase superfamily, lactoperoxidase (LPO) and myeloperoxidase (MPO) share structural and functional features that make them peculiar with respect to other enzymes of the same group. A survey of the available literature on their catalytic intermediates enabled us to ask some questions that remained unanswered. These questions concern controver-sial features of theLPOandMPOcatalytic cycle, suchas the existence of Compound I and Compound II isomers and the identification of their spectroscopic properties....

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  • We have previously reported that two trypsin-like enzymes, acrosin and spermosin, play key roles in sperm penetration through the vitelline coat of the ascidian (Urochordata) Halocynthia roretzi[Sawadaet al. (1984),J. Biol. Chem.259, 2900±2904; Sawadaet al. (1984), Dev. Biol.105, 246±249]. Here, we show the amino-acid sequence of the ascidian preprospermosin, which is deduced from the nucleotide sequence of the isolated cDNA clone.

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  • We live in the age of biology—the human and many other organisms’ genomes have been sequenced and we are starting to understand the function of the metabolic machinery responsible for life on our planet. Thousands of new genes have been discovered, many of these coding for enzymes of yet unknown function. Understanding the kinetic behavior of an enzyme provides clues to its possible physiological role. From a biotechnological point of view, knowledge of the catalytic properties of an enzyme is required for the design of immobilized enzyme-based industrial processes.

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  • - Polysaccharides are macromolecules, polymers with a few hundred to a few thousand monosaccharides joined by glycosidic linkages. - Some polysaccharides serve as storage material, hydrolyzed as needed to provide sugar for cells. - Other polysaccharides serve as building material for structures that protect the cell or the whole organism. - The architecture and function of a polysaccharide are determined by its sugar monomers and by the positions of its glycosidic linkages.

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  • LIFE ON EARTH ULTIMATELY DEPENDS ON ENERGY derived from the sun. Photosynthesis is the only process of biological importance that can harvest this energy. In addition, a large fraction of the planet’s energy resources results from photosynthetic activity in either recent or ancient times (fossil fuels). This chapter introduces the basic physical principles that underlie photosynthetic energy storage and the current understanding of the structure and function of the photosynthetic apparatus (Blankenship 2002). The term photosynthesis means literally “synthesis using light.

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  • Metabolism ofD-amino acids is of considerable interest due to their key importance in cell structure and function. Salmonella typhimuriumD-serine deaminase (StDSD) is a pyridoxal 5¢ phosphate (PLP) dependent enzyme that catalyses degradation of D-Ser to pyruvate and ammonia.

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  • 3-carboxy-cis,cis-muconate lactonizing enzymes participate in the protoca-techuate branch of the 3-oxoadipate pathway of various aerobic bacteria. The gene encoding a 3-carboxy-cis,cis-muconate lactonizing enzyme (pcaB1S2) was cloned from a gene cluster involved in protocatechuate deg-radation by Agrobacterium radiobacterstrain S2.

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  • The bifunctional enzyme glucose-6-phosphate dehydrogenase-6-phospho-gluconolactonase (G6PD-6PGL) found in Plasmodium falciparum has unique structural and functional characteristics restricted to this genus. This study was designed to examine the effects of RNA-mediated PfG6PD-6PGL gene silencing in cultures ofP. falciparumon the expression of para-site antioxidant defense genes at the transcription level.

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  • The use ofBacillus amyloliquefaciensfor enzyme production and its exceptional highprotein export capacity initiated this study where the presence and function of multiple type I signal peptidase isoforms was investigated. In addition to type I signal peptidases SipS(ba) [Meijer,W.J.J., de Jong,A., Bea, G., Wisman, A., Tjalsma, H., Venema, G., Bron, S. & van Dijl, J.M. (1995)Mol. Microbiol.17, 621±631] and SipT(ba) [Hoang, V. & Hofemeister, J. (1995) Biochim. Biophys.

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  • The enzyme fumarase is a conserved protein in all organisms with regard to its sequence, structure and function. This enzyme participates in the tri-carboxylic acid cycle in mitochondria which is essential for cellular respira-tion in eukaryotes.

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  • The lactate dehydrogenase enzyme fromPlasmodium falciparum(PfLDH) is a target for antimalarial compounds owing to structural and functional differences from the human isozymes. The plasmodial enzyme possesses a five-residue insertion in the substrate-specificity loop and exhibits less marked substrate inhibition than its mammalian counterparts.

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  • The effects of high hydrostatic pressure (HHP) and urea on conformational transitions of humana-thrombin structure were studiedbyfluorescence spectroscopy andbymeasuring the catalytic activity of the enzyme. Treatment of thrombin with urea produced a progressive red shift in the center of mass of the intrinsic fluorescence emission spectrum, with a maximum displacement of 650 cm )1 . HHP (270 MPa) shifted the centre ofmass by only 370 cm )1 .HHP combined with a subdenaturing urea concentration (1.5M) displaced the centre of mass by 750 cm )1 ....

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