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https://www.readbyqxmd.com/read/28737940/defining-the-structural-basis-for-allosteric-product-release-from-e-coli-dihydrofolate-reductase-using-nmr-relaxation-dispersion
#1
David Oyen, R Bryn Fenwick, Phillip C Aoto, Robyn L Stanfield, Ian A Wilson, H Jane Dyson, Peter E Wright
The rate-determining step in the catalytic cycle of E.coli dihydrofolate reductase is tetrahydrofolate (THF) product release, which can occur via an allosteric or an intrinsic pathway. The allosteric pathway, which becomes accessible when the reduced cofactor NADPH is bound, involves transient sampling of a higher energy conformational state, greatly increasing the product dissociation rate compared to the intrinsic pathway that obtains when NADPH is absent. Although the kinetics of this process are known, the enzyme structure and the THF product conformation in the transiently formed excited state remains elusive...
July 24, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28707064/development-of-a-lateral-flow-dipstick-immunoassay-for-evaluation-of-folate-levels-in-maize
#2
Qiuju Liang, Chen Yi, Ling Jiang, Guiyu Tan, Chunyi Zhang, Baomin Wang
Folates (vitamin B9) are essential for all organisms as cofactors for one-carbon metabolism. However, measurement of folates is technically complicated and time-consuming. In this study, we developed a dipstick immunoassay using a folate-specific monoclonal antibody (mAb), allowing rapid and low-cost detection of folates. The indicator range of the dipstick for 5-formylterahydrofolate (5-CHO-THF), 5-methyltetrahydrofolate (5-CH3-THF) and their polyglutamyl forms was 100-200 ng mL(-1); moreover, no cross-reactivity was observed with tetrahydrofolate (THF) or 5,10-methenyltetrahydrofolate (5,10-CH=THF) at 500 ng mL(-1), or with the folate precursors pterin-6-COOH, p-aminobenzoate (pABA), and L-glutamate, or with the folate analogues methotrexate and 10-formyltetrahydrofolate (10-CHO-THF) at up to 1000 ng mL(-1)...
July 13, 2017: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/28540433/altered-tetrahydrobiopterin-metabolism-in-patients-with-phenylalanine-hydroxylase-deficiency
#3
Francesca Nardecchia, Flavia Chiarotti, Claudia Carducci, Silvia Santagata, Giulia Valentini, Antonio Angeloni, Nenad Blau, Vincenzo Leuzzi
The tetrahydrobiopterin (BH4) cofactor is essential for the activity of various enzymes, including phenylalanine (Phe) hydroxylase. In phenylketonuria (PKU) patients, who are chronically exposed to high Phe levels, high urinary excretion of BH4 metabolites neopterin and biopterin is observed. The aim of this longitudinal study was to investigate consistence and variability of the urinary excretion of pterins (neopterin and biopterin) in PKU patients in relation to age and concomitant blood Phe and tyrosine levels...
May 24, 2017: European Journal of Pediatrics
https://www.readbyqxmd.com/read/28496149/the-active-site-structure-and-catalytic-mechanism-of-arsenite-oxidase
#4
Thomas P Warelow, M Jake Pushie, Julien J H Cotelesage, Joanne M Santini, Graham N George
Arsenite oxidase is thought to be an ancient enzyme, originating before the divergence of the Archaea and the Bacteria. We have investigated the nature of the molybdenum active site of the arsenite oxidase from the Alphaproteobacterium Rhizobium sp. str. NT-26 using a combination of X-ray absorption spectroscopy and computational chemistry. Our analysis indicates an oxidized Mo(VI) active site with a structure that is far from equilibrium. We propose that this is an entatic state imposed by the protein on the active site through relative orientation of the two molybdopterin cofactors, in a variant of the Rây-Dutt twist of classical coordination chemistry, which we call the pterin twist hypothesis...
May 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28485428/exploring-micropollutant-biotransformation-in-three-freshwater-phytoplankton-species
#5
Michael A Stravs, Francesco Pomati, Juliane Hollender
Phytoplankton constitute an important component of surface water ecosystems; however little is known about their contribution to biotransformation of organic micropollutants. To elucidate biotransformation processes, batch experiments with two cyanobacterial species (Microcystis aeruginosa and Synechococcus sp.) and one green algal species (Chlamydomonas reinhardtii) were conducted. Twenty-four micropollutants were studied, including 15 fungicides and 9 pharmaceuticals. Online solid phase extraction (SPE) coupled with liquid chromatography (LC)-high resolution tandem mass spectrometry (HRMS/MS) was used together with suspect and nontarget screening to identify transformation products (TPs)...
June 21, 2017: Environmental Science. Processes & Impacts
https://www.readbyqxmd.com/read/28480921/electronic-relaxation-pathways-of-the-biologically-relevant-pterin-chromophore
#6
R M DiScipio, R Y Santiago, D Taylor, C E Crespo-Hernández
Pterin derivatives are endogenous photosensitizers common to every biological kingdom and are involved in numerous photobiological processes for which they have received widespread attention. Despite the photobiological relevance of the pterin compounds, their excited-state dynamics have not been investigated rigorously-an undertaking that must begin with a thorough understanding of the photophysics of the common core chromophore, 2-amino-1H-pteridin-4-one (a.k.a. pterin). In this contribution, direct observation of the ultrafast excited-state dynamics of pterin in aqueous borate buffered solution at pH 10...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28463009/lipophilic-decyl-chain-pterin-conjugates-with-sensitizer-properties
#7
Mariana Vignoni, Niluksha Walalawela, Sergio Mauricio Bonesi, Alexander Greer, Andrés Héctor Thomas
A new series of decyl chain [-(CH2)9CH3] pterin conjugates have been investigated by photochemical and photophysical methods, and with theoretical solubility calculations. To synthesize the pterins, a nucleophilic substitution (S(N)2) reaction was used for the regioselective coupling of the alkyl chain to the O site over the N(3) site. However, the O-alkylated pterin converts to N(3)-alkylated pterin under basic conditions, pointing to a kinetic product in the former and a thermodynamic product in the latter...
May 2, 2017: Molecular Pharmaceutics
https://www.readbyqxmd.com/read/28460363/simplified-hplc-methodology-for-quantifying-biological-pterins-by-selective-oxidation
#8
Cristian Valdés, Diego Arauna, Daniel González, Jorge Villaseñor
Tetrahydrobiopterin (BH4) has become a potential therapeutic tool to treat cardiovascular diseases, since it is an essential cofactor of nitric oxide synthase. In order to quantify the amount of BH4 and its related biopterins, a procedure that involves differential oxidation is currently used, which measures biopterin (the product of the oxidation of BH4 and BH2) at two different pH conditions to calculate the quantity of BH2 and BH4, using high performance liquid chromatography (HPLC). In this work, a method was established in order to quantify BH4 and BH2 by adapting previously described procedures...
June 15, 2017: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
https://www.readbyqxmd.com/read/28431213/genome-mining-unearths-a-hybrid-nonribosomal-peptide-synthetase-like-pteridine-synthase-biosynthetic-gene-cluster
#9
Hyun Bong Park, Corey E Perez, Karl W Barber, Jesse Rinehart, Jason M Crawford
Nonribosomal peptides represent a large class of metabolites with pharmaceutical relevance. Pteridines, such as pterins, folates, and flavins, are heterocyclic metabolites that often serve as redox-active cofactors. The biosynthetic machineries for construction of these distinct classes of small molecules operate independently in the cell. Here, we discovered an unprecedented nonribosomal peptide synthetase-like-pteridine synthase hybrid biosynthetic gene cluster in Photorhabdus luminescens using genome synteny analysis...
March 15, 2017: ELife
https://www.readbyqxmd.com/read/28330952/effects-of-insulin-and-the-glucagon-like-peptide-1-receptor-agonist-liraglutide-on-the-kidney-proteome-in-db-db-mice
#10
Leena Liljedahl, Jenny Norlin, James N McGuire, Peter James
Diabetes mellitus (DM) is a worldwide disease that affects 9% of the adult world population and type 2 DM accounts for 90% of those. A common consequence of DM is kidney complications, which could lead to kidney failure. We studied the potential effects of treatment with insulin and the glucagon-like peptide 1 receptor (GLP-1R) agonist liraglutide on the diabetic kidney proteome through the use of the db/db mouse model system and mass spectrometry (MS). Multivariate analyses revealed distinct effects of insulin and liraglutide on the db/db kidney proteome, which was seen on the protein levels of, for example, pterin-4 α-carbinolamine dehydratase/dimerization cofactor of hepatocyte nuclear factor-1α (PCBD1), neural precursor cell expressed developmentally down-regulated-8 (NEDD8), transcription elongation factor-B polypeptide-1 (ELOC) and hepcidin (HEPC)...
March 2017: Physiological Reports
https://www.readbyqxmd.com/read/28284389/biochemical-analyses-of-cerebrospinal-fluid-for-the-diagnosis-of-neurometabolic-conditions-what-can-we-expect
#11
Marta Batllori, Marta Molero-Luis, Mercedes Casado, Cristina Sierra, Rafael Artuch, Aida Ormazabal
In this article, we review the state-of-the-art analysis of different biomarkers in the cerebrospinal fluid for the diagnosis of genetically conditioned, rare, neurometabolic diseases, including glucose transport defects, neurotransmitter (dopamine, serotonin, and gamma-aminobutyric acid) and pterin deficiencies, and vitamin defects (folate, vitamin B6, and thiamine) that affect the brain. The analysis of several key metabolites are detailed, which thus highlights the preanalytical and analytical factors that should be cautiously controlled to avoid misdiagnosis; moreover, these factors may facilitate an adequate interpretation of the biochemical profiles in the context of severe neuropediatric disorders...
November 2016: Seminars in Pediatric Neurology
https://www.readbyqxmd.com/read/28057123/-ptps-gene-analysis-and-prenatal-diagnosis-in-patients-with-6-pyruvoyl-tetra-hydropterin-synthase-deficiency
#12
N Liu, D H Zhao, X L Li, L X Cui, Q H Wu, M Jiang, X D Kong
Objective: To analyze the variations of PTPS gene in patients with suspected 6-pyruvoyl-tetra hydropterin synthase deficiency (PTPSD) and to make prenatal diagnosis in high-risk families. Methods: Chemiluminescence was used for phenylalanine detection in blood or dried blood spots.Patients with phenylalanine concentration over 120 μmol/L were detected by urine pterin analysis, and the activity of dihydropteridine reductase (DHPR) was detected. tetrahydrobiopterin loading tests were performed in suspected patients with abnormal urinary pterin profiles...
December 25, 2016: Zhonghua Fu Chan Ke za Zhi
https://www.readbyqxmd.com/read/27951651/kinetic-mechanism-and-intrinsic-rate-constants-for-the-reaction-of-a-bacterial-phenylalanine-hydroxylase
#13
Bishnu P Subedi, Paul F Fitzpatrick
The pterin-dependent aromatic amino acid hydroxylases are non-heme iron enzymes that catalyze the hydroxylation of the aromatic side chain of their respective substrates using an Fe(IV)O intermediate. While the eukaryotic enzymes are homotetramers with complex regulatory properties, bacterial phenylalanine hydroxylases are monomers that lack regulatory domains. As a result, the bacterial enzymes are more tractable for mechanistic studies. Using single turnover methods, the complete kinetic mechanism and intrinsic rate constants for Chromobacterium violaceum phenylalanine hydroxylase have been determined with both tetrahydrobiopterin and 6-methyltetrahyropterin as substrates...
December 13, 2016: Biochemistry
https://www.readbyqxmd.com/read/27815627/association-studies-to-transporting-proteins-of-fac-re-i-co-3-pterin-h2o-complex
#14
Fabricio Ragone, Héctor H Martínez Saavedra, Pablo F García, Ezequiel Wolcan, Gerardo A Argüello, Gustavo T Ruiz
A new synthetic route to acquire the water soluble complex fac-Re(I)(CO)3(pterin)(H2O) was carried out in aqueous solution. The complex has been obtained with success via the fac-[Re(I)(CO)3(H2O)3]Cl precursor complex. Re(I)(CO)3(pterin)(H2O) has been found to bind strongly with bovine and human serum albumins (BSA and HSA) with intrinsic-binding constants, Kb, of 6.5 × 10(5) M(-1) and 5.6 × 10(5) M(-1) at 310 K, respectively. The interactions of serum albumins with Re(I)(CO)3(pterin)(H2O) were evaluated employing UV-vis fluorescence and absorption spectroscopy and circular dichroism...
January 2017: Journal of Biological Inorganic Chemistry: JBIC
https://www.readbyqxmd.com/read/27808347/clinical-efficacy-of-melittin-in-the-treatment-of-cats-infected-with-the-feline-immunodeficiency-virus
#15
RANDOMIZED CONTROLLED TRIAL
Anja D Hartmann, Natalie Wilhelm, Volker Erfle, Katrin Hartmann
OBJECTIVE: The bee venom melittin shows an antiviral efficacy against the human immunodeficiency virus in cell culture. It was shown to be non-toxic for cats. Aim of this pilot study was to investigate the clinical efficacy and side-effects of melittin in cats naturally infected with feline immunodeficiency virus (FIV). MATERIAL AND METHODS: The study was performed as a prospective, placebo-controlled double-blinded trial. Twenty cats were included, of which 10 cats each were treated with either melittin (500 µg/kg body weight) or phosphate-buffered saline (placebo) subcutaneously twice per week...
December 5, 2016: Tierärztliche Praxis. Ausgabe K, Kleintiere/Heimtiere
https://www.readbyqxmd.com/read/27693864/acanthamoeba-and-dictyostelium-use-different-foraging-strategies
#16
Nick A Kuburich, Nirakar Adhikari, Jeffrey A Hadwiger
Amoeba often use cell movement as a mechanism to find food, such as bacteria, in their environment. The chemotactic movement of the soil amoeba Dictyostelium to folate or other pterin compounds released by bacteria is a well-documented foraging mechanism. Acanthamoeba can also feed on bacteria but relatively little is known about the mechanism(s) by which this amoeba locates bacteria. Acanthamoeba movement in the presence of folate or bacteria was analyzed in above agar assays and compared to that observed for Dictyostelium...
December 2016: Protist
https://www.readbyqxmd.com/read/27693843/degradation-of-tyrosine-and-tryptophan-residues-of-peptides-by-type-i-photosensitized-oxidation
#17
Carolina Castaño, Mariana Vignoni, Patricia Vicendo, Esther Oliveros, Andrés H Thomas
Pterin derivatives are involved in various biological functions, including enzymatic processes that take place in human skin. Unconjugated oxidized pterins are efficient photosensitizers under UV-A irradiation and accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder. These compounds are able to photoinduce the oxidation of the peptide α-melanocyte-stimulating hormone (α-MSH), which stimulates the production and release of melanin by melanocytes in skin and hair. In the present work we have used two peptides in which the amino acid sequence of α-MSH was mutated to specifically investigate the reactivity of tryptophan (Trp) and tyrosine residues (Tyr)...
November 2016: Journal of Photochemistry and Photobiology. B, Biology
https://www.readbyqxmd.com/read/27666634/pterin-7-carboxamides-as-a-new-class-of-aldose-reductase-inhibitors
#18
Ryota Saito, Saori Suzuki, Kaname Sasaki
Aldose reductase is related to the onset and progression of diabetic complications, such as neuropathy, retinopathy, angiopathy, and so on: therefore molecules that are capable of inhibiting the enzyme are potential drugs for treatment of diabetic complications. Epalrestat is the sole aldose reductase inhibitor that is clinically used, but still has some drawbacks. Thus, the development of new aldose reductase inhibitors is still desired. We have synthesized a series of new pterin-7-carboxamides, and evaluated their in vitro inhibitory activities against human aldose reductase...
October 15, 2016: Bioorganic & Medicinal Chemistry Letters
https://www.readbyqxmd.com/read/27537049/xanthine-dehydrogenase-an-old-enzyme-with-new-knowledge-and-prospects
#19
Cheng-Hua Wang, Chong Zhang, Xin-Hui Xing
Xanthine dehydrogenase (EC 1.17.1.4, XDH) is a typical and complex molybdenum-containing flavoprotein which has been extensively studied for over 110 years. This enzyme catalyzes the oxidation of purines, pterin and aldehydes with NAD(+) or NADP(+) as electron acceptor, and sometimes can be transformed to xanthine oxidase (EC 1.17.3.2, XOD) capable of utilizing oxygen as the electron acceptor. XDHs are widely distributed in all eukarya, bacteria and archaea domains, and are proposed to play significant roles in various cellular processes, including purine catabolism and production of reactive oxygen species (ROS) and nitric oxide (NO) in both physiological and pathological contexts...
November 2016: Bioengineered
https://www.readbyqxmd.com/read/27500308/photooxidation-of-tryptophan-and-tyrosine-residues-in-human-serum-albumin-sensitized-by-pterin-a-model-for-globular-protein-photodamage-in-skin
#20
Lara O Reid, Ernesto A Roman, Andrés H Thomas, M Laura Dántola
Human serum albumin (HSA) is the most abundant protein in the circulatory system. Oxidized albumin was identified in the skin of patients suffering from vitiligo, a depigmentation disorder in which the protection against ultraviolet (UV) radiation fails because of the lack of melanin. Oxidized pterins, efficient photosensitizers under UV-A irradiation, accumulate in the skin affected by vitiligo. In this work, we have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to induce structural and chemical changes in HSA under UV-A irradiation...
August 30, 2016: Biochemistry
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