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Enzyme kinetics

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https://www.readbyqxmd.com/read/29793143/oxidation-at-c-16-enhances-butyrylcholinesterase-inhibition-in-lupane-triterpenoids
#1
María Julia Castro, Victoria Richmond, María Belén Faraoni, Ana Paula Murray
A set of triterpenoids with different grades of oxidation in the lupane skeleton were prepared and evaluated as cholinesterase inhibitors. Allylic oxidation with selenium oxide and Jones's oxidation were employed to obtain mono-, di- and tri-oxolupanes, starting from calenduladiol (1) and lupeol (3). All the derivatives showed a selective inhibition of butyrylcholinesterase over acetylcholinesterase (BChE vs. AChE). A kinetic study proved that compounds 2 and 9, the more potent inhibitors of the series, act as competitive inhibitors...
May 17, 2018: Bioorganic Chemistry
https://www.readbyqxmd.com/read/29793040/quinones-and-nitroaromatic-compounds-as-subversive-substrates-of-staphylococcus-aureus-flavohemoglobin
#2
Myriam Moussaoui, Lina Misevičienė, Žilvinas Anusevičius, Audronė Marozienė, Florence Lederer, Laura Baciou, Narimantas Čėnas
In microorganisms, flavohemoglobins (FHbs) containing FAD and heme (Fe3+ , metHb) convert NO. into nitrate at the expense of NADH and O2 . FHbs contribute to bacterial resistance to nitrosative stress. Therefore, inhibition of FHbs functions may decrease the pathogen virulence. We report here a kinetic study of the reduction of quinones and nitroaromatic compounds by S. aureus FHb. We show that this enzyme rapidly reduces quinones and nitroaromatic compounds in a mixed single- and two-electron pathway. The reactivity of nitroaromatics increased upon an increase in their single-electron reduction potential (E1 7 ), whereas the reactivity of quinones poorly depended on their E1 7 with a strong preference for a 2-hydroxy-1,4-naphthoquinone structure...
May 21, 2018: Free Radical Biology & Medicine
https://www.readbyqxmd.com/read/29793023/kinetics-and-stereochemistry-of-linb-catalyzed-%C3%AE-hbcd-transformation-comparison-of-in-vitro-and-in-silico-results
#3
Norbert V Heeb, Manuel Mazenauer, Simon Wyss, Birgit Geueke, Hans-Peter E Kohler, Peter Lienemann
LinB is a haloalkane dehalogenase found in Sphingobium indicum B90A, an aerobic bacterium isolated from contaminated soils of hexachlorocyclohexane (HCH) dumpsites. We showed that this enzyme also converts hexabromocyclododecanes (HBCDs). Here we give new insights in the kinetics and stereochemistry of the enzymatic transformation of δ-HBCD, which resulted in the formation of two pentabromocyclododecanols (PBCDols) as first- (P1δ , P2δ ) and two tetrabromocyclododecadiols (TBCDdiols) as second-generation products (T1δ , T2δ )...
May 12, 2018: Chemosphere
https://www.readbyqxmd.com/read/29792957/high-activity-production-of-xylanase-by-pichia-stipitis-purification-characterization-kinetic-evaluation-and-xylooligosaccharides-production
#4
Changhe Ding, Mengxing Li, Yuqi Hu
As an industrially important biological macromolecule, xylanase hydrolyzes xylan to produce xylooligosaccarides (XOS). XOS, with a degree of polymerization (DP) 2 to 4, are important prebiotics used as food ingredients. In this study, xylanase (5536 U/g substrate) was produced by Pichia stipitis using corncob and wheat bran mixture under solid state fermentation. Crude xylanase were purified and biochemically characterized. XOS hydrolyzed by crude and purified xylanases were quantified. Molecular weight of the purified enzyme was around 31...
May 21, 2018: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/29792900/the-sulfoconjugation-of-androstenone-and-dehydroepiandrosterone-by-human-and-porcine-sulfotransferase-enzymes
#5
Heidi Laderoute, Christine Bone, E James Squires
Porcine sulfotransferase 2A1 (pSULT2A1) is a key enzyme involved in the testicular and hepatic sulfoconjugation of steroids such as dehydroepiandrosterone (DHEA) and potentially androstenone. This latter steroid is a major cause of boar taint, which is an unpleasant off-odour and off-flavour in pork from male pigs. Sulfotransferase 2B1 (pSULT2B1) may also be important, although no direct evidence exists for its involvement in sulfoconjugation of steroids. The purpose of this study was to investigate the sulfoconjugation activity of human and porcine sulfotransferases towards DHEA and androstenone...
May 21, 2018: Steroids
https://www.readbyqxmd.com/read/29792689/selectivity-within-a-family-of-bacterial-phosphothreonine-lyases
#6
Kaitlin A Chambers, Nile S Abularrage, Rebecca A Scheck
Phosphothreonine lyases are bacterial effector proteins secreted into host cells to facilitate the infection process. This enzyme family catalyzes an irreversible elimination reaction that converts phosphothreonine or phosphoserine to dehydrobutyrine or dehydroalanine, respectively. Herein we report a study of substrate selectivity for each of the four known phosphothreonine lyases. This was accomplished using a combination of mass spectrometry and enzyme kinetics assays for a series of phosphorylated peptides derived from the mitogen activated protein kinase (MAPK) activation loop...
May 24, 2018: Biochemistry
https://www.readbyqxmd.com/read/29792416/phosphotriesterase-magnetic-nanoparticles-bioconjugates-with-improved-enzyme-activity-in-a-biocatalytic-membrane-reactor
#7
Abaynesh Yihdego Gebreyohannes, Rosalinda Mazzei, Mohamed Yahia Marei Abdelrahim, Giuseppe Vitola, Elena Porzio, Giuseppe Manco, Mihail Barboiu, Lidietta Giorno
The need to find alternative bioremediation solutions for organophosphate degradation pushed the research to develop technologies based on organophosphate degrading enzymes, such as phosphotriesterase. The use of free phosphotriesterase poses limits in terms of enzyme reuse, stability and process development. The heterogenization of enzyme on a support and their use in bioreactors implemented by membrane seems a suitable strategy, thanks to the ability of membranes to compartmentalize, to govern mass transfer and provide microenvironment with tuned physico-chemical and structural properties...
May 24, 2018: Bioconjugate Chemistry
https://www.readbyqxmd.com/read/29792149/inhibition-of-mutated-isocitrate-dehydrogenase-1-in-cancer
#8
Fangrui Wu, Gang Cheng, Yuan Yao, Mari Kogiso, Hong Jiang, Xiao-Nan Li, Yongcheng Song
BACKGROUND: R132H mutation of isocitrate dehydrogenase 1 (IDH1) are found in ~75% of low-grade gliomas and secondary glioblastomas as well as in several other types of cancer. More chemotypes of inhibitors of IDH1(R132H) are therefore needed. OBJECTIVE: To develop a new class of IDH1(R132H) inhibitors as potent antitumor agents. METHOD: A biochemical assay was developed to find inhibitors of IDH1(R132H) mutant enzyme. Chemical synthesis and structure activity relationship studies were used to find compounds with improved potency...
May 23, 2018: Medicinal Chemistry
https://www.readbyqxmd.com/read/29792035/3-substituted-1-5-diaryl-1-h-1-2-4-triazoles-as-prospective-pet-radioligands-for-imaging-brain-cox-1-in-monkey-part-2-selection-and-evaluation-of-11c-ps13-for-quantitative-imaging
#9
Stal Shrestha, Prachi Singh, Michelle Y Cortes-Salva, Kimberly J Jenko, Masamichi Ikawa, Min-Jeong Kim, Masato Kobayashi, Cheryl L Morse, Robert L Gladding, Jeih-San Liow, Sami S Zoghbi, Masahiro Fujita, Robert B Innis, Victor W Pike
In our preceding paper (Part 1), we identified three 1,5-bis-diaryl-1,2,4-triazole-based compounds that merited evaluation as potential PET radioligands for selectively imaging COX-1 in monkey and human brain, namely (1,5-bis-(4-methoxyphenyl)-3-(alkoxy)-1 H -1,2,4-triazoles bearing a 3-methoxy (PS1), a 3-(2,2,2-trifluoroethoxy) (PS13), or a 3-fluoromethoxy substituent (PS2). PS1 and PS13 were labeled by O -11C-methylation reactions with [11C]iodomethane, and PS2 by O -18F-fluoroalkylation with [ d 2-18F]fluorobromomethane...
May 23, 2018: ACS Chemical Neuroscience
https://www.readbyqxmd.com/read/29786938/inhibition-and-kinetic-studies-of-lignin-degrading-enzymes-of-ganoderma-boninense-by-naturally-occurring-phenolic-compounds
#10
Arthy Surendran, Yasmeen Siddiqui, Halimi Mohd Saud, Nusaibah Syd Ali, Sivakumar Manickam
AIM: Lignolytic (Lignin degrading) enzyme, from oil palm pathogen Ganoderma boninense Pat. (Syn G. orbiforme (Ryvarden), is involved in the detoxification and the degradation of lignin in the oil palm and is the rate-limiting step in the infection process of this fungus. Active inhibition of lignin degrading enzymes secreted by G. boninense by various naturally occurring phenolic compounds and estimation of efficiency on pathogen suppression was aimed at. METHODS AND RESULTS: In our work, ten naturally occurring phenolic compounds were evaluated for their inhibitory potential towards the lignolytic enzymes of G...
May 22, 2018: Journal of Applied Microbiology
https://www.readbyqxmd.com/read/29786669/protein-tyrosine-phosphatase-1b-inhibition-and-glucose-uptake-potentials-of-mulberrofuran-g-albanol-b-and-kuwanon-g-from-root-bark-of-morus-alba-l-in-insulin-resistant-hepg2-cells-an-in-vitro-and-in-silico-study
#11
Pradeep Paudel, Ting Yu, Su Hui Seong, Eun Bi Kuk, Hyun Ah Jung, Jae Sue Choi
Type II diabetes mellitus (T2DM) is the most common form of diabetes and has become a major health problem across the world. The root bark of Morus alba L. is widely used in Traditional Chinese Medicine for treatment and management of diabetes. The aim of the present study was to evaluate the enzyme inhibitory potentials of three principle components, mulberrofuran G ( 1 ), albanol B ( 2 ), and kuwanon G ( 3 ) in M. alba root bark against diabetes, establish their enzyme kinetics, carry out a molecular docking simulation, and demonstrate the glucose uptake activity in insulin-resistant HepG2 cells...
May 22, 2018: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/29785432/molecular-insights-into-avibactam-mediated-class-c-%C3%AE-lactamase-inhibition-competition-between-reverse-acylation-and-hydrolysis-through-desulfation
#12
Chandan Kumar Das, Nisanth N Nair
Avibactam is one of the promising next generation β-lactamase inhibitors due to its exceptional inhibition against wide-spectrum serine β-lactamases. The unusual reversible acylation mechanism has particularly gained interest to explain the inhibition mechanism of avibactam. We explore the mechanism of acylation and deacylation involving avibactam in class-C β-lactamases (CBLs) through hybrid quantum mechanical/molecular mechanical (QM/MM) enhanced sampling molecular dynamics (MD) simulations. Based on these computations, we probe the kinetic stability of the acyl-enzyme complex formed by avibactam and CBLs, thereby gaining molecular level insights into the avibactam-mediated inhibition of CBLs...
May 22, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29784851/replacement-by-site-saturation-mutagenesis-of-residue-119-in-ndm-1-metallo-%C3%AE-lactamase-a-kinetic-study
#13
Francesca Marcoccia, Paola Sandra Mercuri, Moreno Galleni, Giuseppe Celenza, Gianfranco Amicosante, Mariagrazia Perilli
NDM-1 is a subclass B1 metallo-β-lactamase which exhibits a broad activity spectrum against β-lactam antibiotics. In this study we report the kinetic study of six Q119X variants obtained by site-directed mutagenesis on NDM-1. All Q119X variants were able to hydrolyze very efficiently carbapenems, penicillins and 1st , 2nd , 3rd and 4th generation cephalosporins. In particular, Q119E, Q119Y, Q119V and Q119K mutants showed an improvement of kcat/ Km towards penicillins respect to NDM-1. The catalytic efficiency of Q119K variant is about 65- and 70-fold higher than that of NDM-1 for benzylpenicillin and carbenicillin, respectively...
May 21, 2018: Antimicrobial Agents and Chemotherapy
https://www.readbyqxmd.com/read/29784813/coordination-of-the-leucine-sensing-rag-gtpase-cycle-by-leucyl-trna-synthetase-in-the-mtorc1-signaling-pathway
#14
Minji Lee, Jong Hyun Kim, Ina Yoon, Chulho Lee, Mohammad Fallahi Sichani, Jong Soon Kang, Jeonghyun Kang, Min Guo, Kang Young Lee, Gyoonhee Han, Sunghoon Kim, Jung Min Han
A protein synthesis enzyme, leucyl-tRNA synthetase (LRS), serves as a leucine sensor for the mechanistic target of rapamycin complex 1 (mTORC1), which is a central effector for protein synthesis, metabolism, autophagy, and cell growth. However, its significance in mTORC1 signaling and cancer growth and its functional relationship with other suggested leucine signal mediators are not well-understood. Here we show the kinetics of the Rag GTPase cycle during leucine signaling and that LRS serves as an initiating "ON" switch via GTP hydrolysis of RagD that drives the entire Rag GTPase cycle, whereas Sestrin2 functions as an "OFF" switch by controlling GTP hydrolysis of RagB in the Rag GTPase-mTORC1 axis...
May 21, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29784784/uncovering-universal-rules-governing-the-selectivity-of-the-archetypal-dna-glycosylase-tdg
#15
Thomas Dodd, Chunli Yan, Bradley R Kossmann, Kurt Martin, Ivaylo Ivanov
Thymine DNA glycosylase (TDG) is a pivotal enzyme with dual roles in both genome maintenance and epigenetic regulation. TDG is involved in cytosine demethylation at CpG sites in DNA. Here we have used molecular modeling to delineate the lesion search and DNA base interrogation mechanisms of TDG. First, we examined the capacity of TDG to interrogate not only DNA substrates with 5-carboxyl cytosine modifications but also G:T mismatches and nonmismatched (A:T) base pairs using classical and accelerated molecular dynamics...
May 21, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29784728/cyp2d6-allelic-variants-34-17-2-17-3-and-53-and-a-thr309ala-mutant-display-altered-kinetics-and-nadph-coupling-in-metabolism-of-bufuralol-and-dextromethorphan-and-altered-susceptibility-to-inactivation-by-sch-66712
#16
Sarah M Glass, Cydney M Martell, Alexandria K Oswalt, Victoria Osorio-Vasquez, Christi Cho, Michael J Hicks, Jacqueline M Mills, Rina Fujiwara, Michael J Glista, Sharat S Kamath, Laura Lowe Furge
Metabolic phenotype can be affected by multiple factors including allelic variation and interactions with inhibitors. Human CYP2D6 is responsible for approximately 20% of CYP-mediated drug metabolism but consists of over 100 known variants with several variants being commonly found in the population and others quite rare. Four CYP2D6 allelic variants - three with a series of mutations distal to the active site (*34, *17-2, *17-3) and one ultra-metabolizer with mutations near the active site (*53), along with reference *1 and an active site mutant of *1 (Thr309Ala) were expressed, purified, and studied for interactions with the typical substrates dextromethorphan and bufuralol and the inactivator SCH 66712...
May 21, 2018: Drug Metabolism and Disposition: the Biological Fate of Chemicals
https://www.readbyqxmd.com/read/29783967/characterization-of-a-novel-thermostable-and-xylose-tolerant-gh-39-%C3%AE-xylosidase-from-dictyoglomus-thermophilum
#17
Qi Li, Tao Wu, Zhipeng Qi, Linguo Zhao, Jianjun Pei, Feng Tang
BACKGROUND: β-D-xylosidase is a vital exoglycosidase with the ability to hydrolyze xylooligosaccharides to xylose and to biotransform some saponins by cleaving outer β-xylose. β-D-xylosidase is widely used as one of the xylanolytic enzymes in a diverse range of applications, such as fuel, food and the pharmaceutical industry; therefore, more and more studies have focused on the thermostable and xylose-tolerant β-D-xylosidases. RESULTS: A thermostable β-xylosidase gene (xln-DT) of 1509 bp was cloned from Dictyoglomus thermophilum and expressed in E...
May 21, 2018: BMC Biotechnology
https://www.readbyqxmd.com/read/29783045/factors-affecting-gene-expression-and-activity-of-heme-and-manganese-dependent-catalases-in-lactobacillus-casei-strains
#18
Annamaria Ricciardi, Rocco Gerardo Ianniello, Eugenio Parente, Teresa Zotta
Catalases reduce oxidative stress by degrading hydrogen peroxide to molecular oxygen and water. The presence of heme-dependent or manganese-dependent catalases was observed for a long time in lactic acid bacteria (LAB) but, to date, knowledge on the factors affecting gene expression and enzymatic functionality are limited to a very few strains. In this study, the effect of atmosphere of incubation (not aerated static growth vs aerated shaken growth) and supplementation with Fe2+ , hemin, Mn2+ or their combinations on the catalase production of respiration-competent strain Lactobacillus casei N87 was evaluated using a 24 factorial design...
May 8, 2018: International Journal of Food Microbiology
https://www.readbyqxmd.com/read/29782976/ldiscu-is-a-2fe-2s-scaffold-protein-which-interacts-with-ldiscs-and-its-expression-is-modulated-by-fe-s-proteins-in-leishmania-donovani
#19
Krishn Pratap Singh, Shadab Anwar, Amir Zaidi, Kuljit Singh, Pradeep Das, Samudrala Gourinath, Vahab Ali
The pathogenicity of protozoan parasites is frequently attributed to their ability to circumvent the deleterious effects of ROS and Fe-S clusters are among their susceptible targets with paramount importance for parasite survival. The biogenesis of Fe-S clusters is orchestrated by ISC system; the sulfur donor IscS and scaffold protein IscU being its core components. However, among protozoan parasites including Leishmania, no information is available regarding biochemical aspect of IscU, its interaction partners and regulation...
May 18, 2018: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/29782674/molecularly-imprinted-porous-aromatic-frameworks-serving-as-porous-artificial-enzymes
#20
Ye Yuan, Yajie Yang, Muhammad Faheem, Xiaoqin Zou, Xujiao Ma, Zeyu Wang, Qinghao Meng, Lili Wang, Shuai Zhao, Guangshan Zhu
Artificially designed enzymes are in demand as ideal catalysts for industrial production but their dense structure conceals most of their functional fragments, thus detracting from performance. Here, molecularly imprinted porous aromatic frameworks (MIPAFs) which are exploited to incorporate full host-guest interactions of porous materials within the artificial enzymes are presented. By decorating a porous skeleton with molecularly imprinted complexes, it is demonstrated that MIPAFs are porous artificial enzymes possessing excellent kinetics for guest molecules...
May 21, 2018: Advanced Materials
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