keyword
MENU ▼
Read by QxMD icon Read
search

Enzyme kinetics

keyword
https://www.readbyqxmd.com/read/28651322/ozonation-of-tannic-acid-to-model-biomass-pretreatment-for-bioethanol-production
#1
Roi Peretz, Yoram Gerchman, Hadas Mamane
Lignocellulosic biomass is a promising feedstock for ethanol production, but lignin, a polyphenol, hampers the use of enzymes for its saccharification; pretreatment is thus key to preparing such feedstock. Ozonation was previously demonstrated as an effective pretreatment, but claimed to be uneconomical due to the assumed need for lignin mineralization. We analyzed, for the first time, ozonation of highly concentrated tannic acid (TA) solution (60g/L) as a lignin model. Most of the TA disappeared within 3.5h, following triple-phase kinetics with two transition points: at 7min and 60min of ozonation for 0...
June 1, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28651101/competitive-ligands-facilitate-dissociation-of-the-complex-of-bifunctional-inhibitor-and-protein-kinase
#2
Taavi Ivan, Erki Enkvist, Hedi Sinijarv, Asko Uri
Dissociation of the complex of a ligand and a protein usually follows the kinetic profile of the first order process and the rate of dissociation is not affected by the presence of competitive ligands. We discovered that dissociation of the complex between a bifunctional ligand and a protein kinase (the catalytic subunit of cAMP-dependent protein kinase), an enzyme possessing 2 different substrate binding sites, was accelerated (facilitated) over 50-fold in the presence of competitive ligands at higher concentrations...
June 20, 2017: Biophysical Chemistry
https://www.readbyqxmd.com/read/28650657/noncovalent-pegylation-through-protein-polyelectrolyte-interaction-kinetic-experiment-and-molecular-dynamics-simulation
#3
Takaaki Kurinomaru, Kengo Kuwada, Shunsuke Tomita, Tomoshi Kameda, Kentaro Shiraki
Noncovalent binding of polyethylene glycol (PEG) to a protein surface is a unique protein handling technique to control protein function and stability. A diblock copolymer containing PEG and polyelectrolyte chains (PEGylated polyelectrolyte) is a promising candidate for noncovalent attachment of PEG to a protein surface because of the binding through multiple electrostatic interactions without protein denaturation. To obtain a deeper understanding of protein-polyelectrolyte interaction at the molecular level, we investigated the manner in which cationic PEGylated polyelectrolyte binds to anionic α-amylase in enzyme kinetic experiments and molecular dynamics (MD) simulations...
June 26, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28650586/a-complete-thermodynamic-analysis-of-enzyme-turnover-links-the-free-energy-landscape-to-enzyme-catalysis
#4
Hannah Bl Jones, Stephen A Wells, Erica J Prentice, Anthony Kwok, Liyin L Liang, Vickery L Arcus, Christopher R Pudney
Our understanding of how enzymes work is colored by static structure depictions where the enzyme scaffold is presented as either immobile, or in equilibrium between well-defined static conformations. Proteins however exhibit a large degree of motion over a broad range of timescales and magnitudes and this is defined thermodynamically by the enzyme free energy landscape (FEL). The role and importance of enzyme motion is extremely contentious. Much of the challenge is in the experimental detection of so called 'conformational sampling' involved in enzyme turnover...
June 26, 2017: FEBS Journal
https://www.readbyqxmd.com/read/28650006/positional-immobilization-of-pd-nanoparticles-and-enzymes-in-hierarchical-yolk-shell-shell-nanoreactors-for-tandem-catalysis
#5
Xiaoming Zhang, Lingyan Jing, Fangfang Chang, Shuai Chen, Hengquan Yang, Qihua Yang
A hierarchical yolk-shell@shell nanoreactor that spatially positioned Pd nanoparticles and the CALB enzyme in separated domains is constructed, and served as an efficient bifunctional catalyst for the one-pot dynamic kinetic resolution (DKR) reaction of 1-phenylethylamine with excellent activity and selectivity.
June 26, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28648175/enzymatic-phosphorylation-of-mannose-by-glucomannokinase-from-mycobacterium-phlei-using-inorganic-polyphosphate
#6
Shafaq Parveen, Biqiang Chen, Luo Liu, Tianwei Tan
Mannose-6-phosphate is an important phosphor-sugar, which is involved in many physiological functions and it is used to treat many diseases. Its production is however expensive since it requires costly substrate ATP as phosphorylation agent. This study has focused upon the direct synthesis of M6P by glucomannokinase using inorganic polyphosphate without involvement of ATP. The gene cloned for glucomannokinase has been sequenced from Mycobacterium phlei and it is transformed into Escherichia coli for expression...
September 2017: Enzyme and Microbial Technology
https://www.readbyqxmd.com/read/28648071/elucidation-of-the-catalytic-mechanism-of-a-miniature-zinc-finger-hydrolase
#7
Abir Ganguly, Trung Quan Luong, Oliver Brylski, Michael Dirkmann, David Möller, Simon Ebbinghaus, Frank Schulz, Roland Winter, Elsa Sanchez-Garcia, Walter Thiel
To improve our mechanistic understanding of zinc metalloenzymes, we report a joint computational and experimental study of a minimal carbonic anhydrase (CA) mimic, a 22-residue Zn-finger hydrolase. We combine classical molecular dynamics (MD) simulations, quantum mechanics/molecular mechanics (QM/MM) geometry optimizations, and QM/MM free energy simulations with ambient and high-pressure kinetic measurements to investigate the mechanism of the hydrolysis of the substrate p-nitrophenylacetate (pNPA). The zinc center of the hydrolase prefers a pentacoordinated geometry, as found in most naturally occurring CAs and CA-like enzymes...
June 24, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28647665/comparative-metabolism-of-ddao-benzoate-in-liver-microsomes-from-various-species
#8
Hong-Ying Ma, Jia-Da Yang, Jie Hou, Li-Wei Zou, Qiang Jin, Da-Cheng Hao, Jing Ning, Guang-Bo Ge, Ling Yang
DDAB (6,8-dichloro-9,9-dimethyl-7-oxo-7,9-dihydroacridin-2-yl benzoate) is a newly developed near-infrared fluorescent probe for human carboxylesterase 2 (hCE2), exhibiting high specificity and good reactivity for real-time monitoring the enzymatic activities of hCE2 in complex biological systems. In order to explore the applicability of DDAB in commonly used animal species, the interspecies difference in DDAB hydrolysis was carefully investigated by using liver microsomes from human and five experimental animals including mouse, rat, dog, minipig and monkey...
June 21, 2017: Toxicology in Vitro: An International Journal Published in Association with BIBRA
https://www.readbyqxmd.com/read/28646078/stereospecific-metabolism-of-r-and-s-warfarin-by-human-hepatic-cytosolic-reductases
#9
Dustyn A Barnette, Bryce Johnson, Dakota L Pouncey, Robert Nshimiyimana, Linda Desrochers, Thomas E Goodwin, Grover Paul Miller
Coumadin (rac-warfarin) is the most commonly used anticoagulant in the world, yet its clinical use is often challenging due to a narrow therapeutic range and inter-individual variations in response. A critical contributor to the uncertainty is variability in warfarin metabolism, which includes mostly oxidative but also reductive pathways. Reduction of each warfarin enantiomer yields two warfarin alcohol isomers, and the corresponding four alcohols retain varying levels of anticoagulant activity. Studies on the kinetics of warfarin reduction have often lacked resolution of parent drug enantiomers and suffered from co-elution of pairs of alcohol metabolites; thus, those studies fail to establish the importance of individual, stereospecific reductive pathways...
June 23, 2017: Drug Metabolism and Disposition: the Biological Fate of Chemicals
https://www.readbyqxmd.com/read/28645169/heterodimerization-of-arabidopsis-calcium-proton-exchangers-contributes-to-regulation-of-guard-cell-dynamics-and-plant-defense-responses
#10
Bradleigh Hocking, Simon J Conn, Murli Manohar, Bo Xu, Asmini Athman, Matthew A Stancombe, Alex R Webb, Kendal D Hirschi, Matthew Gilliham
Arabidopsis thaliana cation exchangers (CAX1 and CAX3) are closely related tonoplast-localized calcium/proton (Ca2+/H+) antiporters that contribute to cellular Ca2+ homeostasis. CAX1 and CAX3 were previously shown to interact in yeast; however, the function of this complex in plants has remained elusive. Here, we demonstrate that expression of CAX1 and CAX3 occurs in guard cells. Additionally, CAX1 and CAX3 are co-expressed in mesophyll tissue in response to wounding or flg22 treatment, due to the induction of CAX3 expression...
June 22, 2017: Journal of Experimental Botany
https://www.readbyqxmd.com/read/28644760/expression-and-characterization-of-soybean-seed-coat-peroxidase-in-escherichia-coli-bl21-de3
#11
Changqing Liu, Kai Zheng, Ying Xu, Lacmata Tamekou Stephen, Jiming Wang, Hongwei Zhao, Tongqing Yue, Rui Nian, Haibo Zhang, Mo Xian, Huizhou Liu
Soybean seed coat peroxidase(SBP) is a valuable enzyme having a broad variety of applications in analytical chemistry, biochemistry and food processing. In the present study, the sscp gene (Gene ID: 548068) was optimized based on the preferred codon usage of Escherichia coli, synthesized, and expressed in E. coli BL21(DE3). SDS-PAGE and western blot analysis of this expressed protein revealed that its molecular weight is approximately 39 kDa. The effects of induction temperature, concentration of IPTG (isopropyl-β-D-thiogalactoside) and hemin, induction time, expression time were optimized to enhance SBP production with a maximum activity of 11...
June 23, 2017: Preparative Biochemistry & Biotechnology
https://www.readbyqxmd.com/read/28642967/strategies-for-characterization-of-enzymatic-nucleic-acids
#12
Fatemeh Javadi-Zarnaghi, Claudia Höbartner
Practical application of enzymatic nucleic acids has received more attention in recent years. Understanding the mechanism of catalysis and availability of information on potentials and limitations of these enzymes expands their application scope. A general approach for characterization of functional macromolecules including enzymatic nucleic acids is to perturb a specific set of condition and to follow the perturbation effect by biophysical and biochemical methods. This chapter reviews several perturbation strategies for functional nucleic acids, including deletion, mutation, and modifications of backbone and nucleobases, and consequent kinetic analysis, spectroscopic investigations, and probing assays...
June 23, 2017: Advances in Biochemical Engineering/biotechnology
https://www.readbyqxmd.com/read/28642345/evolution-of-nonspectral-rhodopsin-function-at-high-altitudes
#13
Gianni M Castiglione, Frances E Hauser, Brian S Liao, Nathan K Lujan, Alexander Van Nynatten, James M Morrow, Ryan K Schott, Nihar Bhattacharyya, Sarah Z Dungan, Belinda S W Chang
High-altitude environments present a range of biochemical and physiological challenges for organisms through decreases in oxygen, pressure, and temperature relative to lowland habitats. Protein-level adaptations to hypoxic high-altitude conditions have been identified in multiple terrestrial endotherms; however, comparable adaptations in aquatic ectotherms, such as fishes, have not been as extensively characterized. In enzyme proteins, cold adaptation is attained through functional trade-offs between stability and activity, often mediated by substitutions outside the active site...
June 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28642038/functional-characterization-of-21-allelic-variants-of-dihydropyrimidinase
#14
Eiji Hishinuma, Fumika Akai, Yoko Narita, Masamitsu Maekawa, Hiroaki Yamaguchi, Nariyasu Mano, Akifumi Oda, Noriyasu Hirasawa, Masahiro Hiratsuka
Dihydropyrimidinase (DHP, EC 3.5.2.2), encoded by the gene DPYS, is the second enzyme in the catabolic pathway of pyrimidine and of fluoropyrimidine drugs such as 5-fluorouracil, which are commonly used in anticancer treatment; DHP catalyzes the hydrolytic ring opening of dihydrouracil and dihydro-5-fluorouracil. DPYS mutations are known to contribute to interindividual variations in the toxicity of fluoropyrimidine drugs, but the functional characterization of DHP allelic variants remains inadequate. In this study, in vitro analysis was performed on 22 allelic variants of DHP by transiently expressing wild-type DHP and 21 DHP variants in 293FT cells and characterizing their enzymatic activities by using dihydrouracil and dihydro-5-fluorouracil as substrates...
June 19, 2017: Biochemical Pharmacology
https://www.readbyqxmd.com/read/28640753/mechanism-of-antihypertensive-effect-of-mucuna-pruriens-l-seed-extract-and-its-isolated-compounds
#15
Mohammad Yaseen Khan, Vimal Kumar
Background In the search of safe and effective lead molecules from natural sources, Mucuna pruriens (MP) L. (Fabaceae) seeds were utilized for exploring the antihypertensive potential. Traditionally, it is used as diuretic and hypotensive. Methods Bioassay-guided fractions were utilized for the isolation of active compounds by column chromatography. IC50 value, enzyme kinetics and inhibition mechanism were determined. In vivo time and dose-dependent hypotensive study followed by changes in mean arterial pressure (MAP) induced by angiotensin I (3 nmol/kg), angiotensin II (3 nmol/kg), and bradykinin (10 nmol/kg) in anesthetized rats was done...
June 21, 2017: Journal of Complementary & Integrative Medicine
https://www.readbyqxmd.com/read/28640638/enzyme-mediated-conversion-of-fad-to-8-formyl-fad-in-formate-oxidase-results-in-modified-cofactor-with-enhanced-catalytic-properties
#16
John M Robbins, Michael G Souffrant, Donald Hamelberg, Giovanni Gadda, Andreas S Bommarius
Flavins, including flavin adenine dinucleotide (FAD), are fundamental catalytic cofactors responsible for the redox functionality of a diverse set of proteins. Alternatively, modified flavin analogues are rarely found in nature as their incorporation typically results in inactivation of flavoproteins, thus leading to the disruption of important cellular pathways. Here, we report that the fungal flavoenzyme formate oxidase (FOX) catalyzes the slow conversion of non-covalently bound FAD to 8-formyl FAD (8-fFAD), and that this conversion results in a nearly 10-fold increase in formate oxidase activity...
June 22, 2017: Biochemistry
https://www.readbyqxmd.com/read/28639791/insight-into-the-final-step-of-the-supramolecular-buildup-of-eumelanin
#17
Anne Büngeler, Benjamin Hämisch, Klaus Huber, Wolfgang Bremser, Oliver Ingolf Strube
The final step in the supramolecular buildup of eumelanin particles is investigated regarding involved species and mechanism. Time resolved in situ light scattering and scanning electron microscopy reveal an aggregation of particles with narrow size distribution around 40 nm, previously only observed as substructures. These form larger particles with again very uniform size and diameters around 200 nm. Aggregation of each single particle takes only a few minutes to complete, whereas the entire process goes on for at least three hours, partly due to kinetics of the precursors...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28639649/computational-design-of-cephradine-synthase-in-a-new-scaffold-identified-from-structural-databases
#18
Xiaoqiang Huang, Jing Xue, Yushan Zhu
Computational enzyme design exhibits excellent performance for identifying potential scaffolds from structural databases and creating new enzymatic catalysts from naught. Using the active site-matching algorithm ProdaMatch, we identified a new scaffold cocaine esterase from Rhodococcus sp. that showed modest activity (kcat/Km = 0.018 M(-1) s(-1)) towards the hydrolysis of β-lactam antibiotic cephradine. The identified cocaine esterase scaffold afforded low sequence identity (<30%) with the known β-lactam synthases, such as penicillin G acylase or α-amino acid ester hydrolase, and was able to catalyze the condensation reaction between d-dihydrophenylglycine methyl ester and 7-aminodesacetoxycephalosporanic acid to produce cephradine via a kinetically controlled synthesis...
June 22, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28638866/kinetics-of-modulatory-role-of-cyperus-esculentus-l-on-the-specific-activity-of-key-carbohydrate-metabolizing-enzymes
#19
Saheed Sabiu, Emmanuel Oladipo Ajani, Taofik Olatunde Sunmonu, Anofi Omotayo Tom Ashafa
BACKGROUND: The continuous search for new lead compounds as viable inhibitors of specific enzymes linked to carbohydrate metabolism has intensified. Cyperus esculentus L. is one of the therapeutically implicated botanicals against several degenerative diseases including diabetes mellitus. MATERIALS AND METHODS: This study evaluated the antioxidant and mechanism(s) of inhibitory potential of aqueous extract of C. esculentus on α-amylase and α-glucosidase in vitro...
2017: African Journal of Traditional, Complementary, and Alternative Medicines: AJTCAM
https://www.readbyqxmd.com/read/28638761/peroxidase-activity-of-a-c-type-cytochrome%C3%A2-b5-in-the-non-native-state-is-comparable-to-that-of-native-peroxidases
#20
Shan Hu, Bo He, Ke-Jie Du, Xiao-Juan Wang, Shu-Qin Gao, Ying-Wu Lin
The design of artificial metalloenzymes has achieved tremendous progress, although few designs can achieve catalytic performances comparable to that of native enzymes. Moreover, the structure and function of artificial metalloenzymes in non-native states has rarely been explored. Herein, we found that a c-type cytochrome b5 (Cyt b5), N57C/S71C Cyt b5, with heme covalently attached to the protein matrix through two Cys-heme linkages, adopts a non-native state with an open heme site after guanidine hydrochloride (Gdn⋅HCl)-induced unfolding, which facilitates H2O2 activation and substrate binding...
June 2017: ChemistryOpen
keyword
keyword
104582
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"