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https://www.readbyqxmd.com/read/28095695/frontier-molecular-orbital-contributions-to-chlorination-versus-hydroxylation-selectivity-in-the-non-heme-iron-halogenase-syrb2
#1
Martin Srnec, Edward I Solomon
The ability of an Fe(IV)=O intermediate in SyrB2 to perform chlorination vs. hydroxylation was computationally evaluated for different substrates that had been studied experimentally. The π-trajectory for H-atom abstraction (Fe(IV)=O oriented perpendicular to the C-H bond of substrate) was found to lead to the S = 2 five-coordinate HO-Fe(III)-Cl complex with the C• of the substrate, π-oriented relative to both the Cl(-) and OH(-) ligands. From this ferric intermediate, hydroxylation is thermodynamically favored, but chlorination is intrinsically more reactive due to the energy splitting between two key redox-active dπ* frontier molecular orbitals (FMOs)...
January 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28093505/modelling-the-ferrochelatase-c-315-48c-modifier-mutation-for-erythropoietic-protoporphyria-epp-in-mice
#2
Jasmin Barman-Aksözen, Paulina Ćwiek, Vijay B Bansode, Frank Koentgen, Judith Trüb, Pawel Pelczar, Paolo Cinelli, Xiaoye Schneider-Yin, Daniel Schümperli, Elisabeth I Minder
Erythropoietic Protoporphyria (EPP) is caused by deficiency of ferrochelatase (FECH) which incorporates iron into protoporphyrin IX (PPIX) to form heme. Excitation of accumulated PPIX by light generates oxygen radicals which evoke excessive pain and, after longer light exposure, ulcerations in exposed skin areas of EPP patients. Moreover, ∼5% of the patients develop a liver dysfunction due to PPIX accumulation. Most patients (∼97%) have a severe FECH mutation (Mut) in trans to an intronic polymorphism (c...
January 12, 2017: Disease Models & Mechanisms
https://www.readbyqxmd.com/read/28091754/a-new-look-at-the-role-of-thiolate-ligation-in-cytochrome-p450
#3
Timothy H Yosca, Aaron P Ledray, Joanna Ngo, Michael T Green
Protonated ferryl (or iron(IV)hydroxide) intermediates have been characterized in several thiolate-ligated heme proteins that are known to catalyze C-H bond activation. The basicity of the ferryl intermediates in these species has been proposed to play a critical role in facilitating this chemistry, allowing hydrogen abstraction at reduction potentials below those that would otherwise lead to oxidative degradation of the enzyme. In this contribution, we discuss the events that led to the assignment and characterization of the unusual iron(IV)hydroxide species, highlighting experiments that provided a quantitative measure of the ferryl basicity, the iron(IV)hydroxide pKa...
January 16, 2017: Journal of Biological Inorganic Chemistry: JBIC
https://www.readbyqxmd.com/read/28091535/visualization-of-the-role-of-host-heme-on-the-virulence-of-the-heme-auxotroph-streptococcus-agalactiae
#4
Laetitia Joubert, Jean-Baptiste Dagieu, Annabelle Fernandez, Aurélie Derré-Bobillot, Elise Borezée-Durant, Isabelle Fleurot, Alexandra Gruss, Delphine Lechardeur
Heme is essential for several cellular key functions but is also toxic. Whereas most bacterial pathogens utilize heme as a metabolic cofactor and iron source, the impact of host heme during bacterial infection remains elusive. The opportunist pathogen Streptococcus agalactiae does not synthesize heme but still uses it to activate a respiration metabolism. Concomitantly, heme toxicity is mainly controlled by the HrtBA efflux transporter. Here we investigate how S. agalactiae manages heme toxicity versus benefits in the living host...
January 16, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28088643/molecular-mechanisms-of-bio-catalysis-of-heme-extraction-from-hemoglobin
#5
Serzhan Sakipov, Olga Rafikova, Maria G Kurnikova, Ruslan Rafikov
Red blood cell hemolysis in sickle cell disease (SCD) releases free hemoglobin. Extracellular hemoglobin and its degradation products, free heme and iron, are highly toxic due to oxidative stress induction and decrease in nitric oxide availability. We propose an approach that helps to eliminate extracellular hemoglobin toxicity in SCD by employing a bacterial protein system that evolved to extract heme from extracellular hemoglobin. NEAr heme Transporter (NEAT) domains from iron-regulated surface determinant proteins from Staphylococcus aureus specifically bind free heme as well as facilitate its extraction from hemoglobin...
January 7, 2017: Redox Biology
https://www.readbyqxmd.com/read/28080030/chemoselective-enzymatic-c-h-bond-amination-catalyzed-by-a-cytochrome-p450-containing-an-ir-me-pix-cofactor
#6
Pawel Dydio, Hanna M Key, Hiroki Hayashi, Douglas S Clark, John F Hartwig
Cytochrome P450 enzymes have been engineered to catalyze abiological C-H bond amination reactions, but this abiological process is limited by the low chemoselectivity for the amination of C-H bonds over competing reduction of the substrate to a sulfonamide. Here we report that P450s derived from a thermophilic organism and containing an iridium porphyrin cofactor (Ir(Me)-PIX) in place of the heme catalyze C-H bond amination reactions with high chemoselectivity for intramolecular insertion of the resulting nitrenes into C-H bonds over reduction of the azide to the sulfonamide and with broader substrate scope than that of enzymes containing iron porphyrins...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28075024/uncovering-iron-regulation-with-species-specific-transcriptome-patterns-in-atlantic-and-coho-salmon-during-a-caligus-rogercresseyi-infestation
#7
V Valenzuela-Muñoz, S Boltaña, C Gallardo-Escárate
Salmon species cultured in Chile evidence different levels of susceptibility to the sea louse Caligus rogercresseyi. These differences have mainly been associated with specific immune responses. Moreover, iron regulation seems to be an important mechanism to confer immunity during the host infestation. This response called nutritional immunity has been described in bacterial infections, despite that no comprehensive studies involving in marine ectoparasites infestation have been reported. With this aim, we analysed the transcriptome profiles of Atlantic and coho salmon infected with C...
January 11, 2017: Journal of Fish Diseases
https://www.readbyqxmd.com/read/28068331/modelling-systemic-iron-regulation-during-dietary-iron-overload-and-acute-inflammation-role-of-hepcidin-independent-mechanisms
#8
Mihaela Enculescu, Christoph Metzendorf, Richard Sparla, Maximilian Hahnel, Johannes Bode, Martina U Muckenthaler, Stefan Legewie
Systemic iron levels must be maintained in physiological concentrations to prevent diseases associated with iron deficiency or iron overload. A key role in this process plays ferroportin, the only known mammalian transmembrane iron exporter, which releases iron from duodenal enterocytes, hepatocytes, or iron-recycling macrophages into the blood stream. Ferroportin expression is tighly controlled by transcriptional and post-transcriptional mechanisms in response to hypoxia, iron deficiency, heme iron and inflammatory cues by cell-autonomous and systemic mechanisms...
January 9, 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28067471/traditional-and-novel-tools-to-probe-the-mitochondrial-metabolism-in-health-and-disease
#9
REVIEW
Yanfei Zhang, José L Avalos
Mitochondrial metabolism links energy production to other essential cellular processes such as signaling, cellular differentiation, and apoptosis. In addition to producing adenosine triphosphate (ATP) as an energy source, mitochondria are responsible for the synthesis of a myriad of important metabolites and cofactors such as tetrahydrofolate, α-ketoacids, steroids, aminolevulinic acid, biotin, lipoic acid, acetyl-CoA, iron-sulfur clusters, heme, and ubiquinone. Furthermore, mitochondria and their metabolism have been implicated in aging and several human diseases, including inherited mitochondrial disorders, cardiac dysfunction, heart failure, neurodegenerative diseases, diabetes, and cancer...
January 9, 2017: Wiley Interdisciplinary Reviews. Systems Biology and Medicine
https://www.readbyqxmd.com/read/28065861/targeting-and-modulating-infarct-macrophages-with-hemin-formulated-in-designed-lipid-based-particles-improves-cardiac-remodeling-and-function
#10
Tamar Ben-Mordechai, David Kain, Radka Holbova, Natalie Landa, La-Paz Levin, Inbar Elron-Gross, Yifat Glucksam-Galnoy, Micha S Feinberg, Rimona Margalit, Jonathan Leor
Uncontrolled activation of pro-inflammatory macrophages after myocardial infarction (MI) accelerates adverse left ventricular (LV) remodeling and dysfunction. Hemin, an iron-containing porphyrin, activates heme oxygenase-1 (HO-1), an enzyme with anti-inflammatory and cytoprotective properties. We sought to determine the effects of hemin formulated in a macrophage-targeted lipid-based carrier (denoted HA-LP) on LV remodeling and function after MI. Hemin encapsulation efficiency was ~100% at therapeutic dose levels...
January 5, 2017: Journal of Controlled Release: Official Journal of the Controlled Release Society
https://www.readbyqxmd.com/read/28065637/the-steroid-metabolite-16-%C3%AE-oh-androstenedione-generated-by-cyp21a2-serves-as-a-substrate-for-cyp19a1
#11
J Neunzig, M Milhim, L Schiffer, Y Khatri, J Zapp, A Sánchez-Guijo, M F Hartmann, S A Wudy, R Bernhardt
The 21-hydroxylase (CYP21A2) is a steroidogenic enzyme crucial for the synthesis of mineralo- and glucocorticoids. It is described to convert progesterone as well as 17-OH-progesterone, through a hydroxylation at position C21, into 11-deoxycorticosterone (DOC) and 11-deoxycortisol (RSS), respectively. In this study we unraveled CYP21A2 to have a broader steroid substrate spectrum than assumed. Utilizing a reconstituted in vitro system, consisting of purified human CYP21A2 and human cytochrome P450 reductase (CPR) we demonstrated that CYP21A2 is capable to metabolize DOC, RSS, androstenedione (A4) and testosterone (T)...
January 5, 2017: Journal of Steroid Biochemistry and Molecular Biology
https://www.readbyqxmd.com/read/28060867/differential-roles-of-iron-storage-proteins-in-maintaining-the-iron-homeostasis-in-mycobacterium-tuberculosis
#12
Garima Khare, Prachi Nangpal, Anil K Tyagi
Ferritins and bacterioferritins are iron storage proteins that represent key players in iron homeostasis. Several organisms possess both forms of ferritins, however, their relative physiological roles are less understood. Mycobacterium tuberculosis possesses both ferritin (BfrB) and bacterioferritin (BfrA), playing an essential role in its pathogenesis as reported by us earlier. This study provides insights into the role of these two proteins in iron homeostasis by employing M. tuberculosis bfr mutants. Our data suggests that BfrA is required for efficient utilization of stored iron under low iron conditions while BfrB plays a crucial role as the major defense protein under excessive iron conditions...
2017: PloS One
https://www.readbyqxmd.com/read/28055290/heme-and-iron-induce-protein-aggregation
#13
Leonardo H Travassos, Luiz R C Vasconcellos, Marcelo T Bozza, Leticia A M Carneiro
No abstract text is available yet for this article.
January 5, 2017: Autophagy
https://www.readbyqxmd.com/read/28054074/hydroxo-bridged-diiron-iii-and-dimanganese-iii-bisporphyrins-modulation-of-metal-spins-by-counter-anions
#14
Firoz Shah Tuglak Khan, Tapas Guchhait, Sujit Sasmal, Sankar Prasad Rath
The chemistry of oxo/hydroxo-bridged diheme centers, connected covalently through bridges, has attracted much attention recently. Close approach of the two heme centers in the μ-hydroxo complex results in an unequal core deformation which leads to the unusual stabilization of two different spin states of iron in a single molecular framework. The spin states are also counter-anion specific and are reversibly interconvertable. An increased separation between the heme centers, however, leads to a weaker inter-ring interaction and, hence, renders the iron centers equivalent...
January 5, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28053961/iron-supplementation-reverses-the-reduction-of-hydroxymethylcytosine-in-hepatic-dna-associated-with-chronic-alcohol-consumption-in-rats
#15
Stephanie A Tammen, Jung Eun Park, Phil Kyung Shin, Simonetta Friso, Jayong Chung, Sang-Woon Choi
BACKGROUND: Alcohol is known to affect two epigenetic phenomena, DNA methylation and DNA hydroxymethylation, and iron is a cofactor of ten-eleven translocation (TET) enzymes that catalyze the conversion from methylcytosine to hydroxymethylcytosine. In the present study we aimed to determine the effects of alcohol on DNA hydroxymethylation and further effects of iron on alcohol associated epigenetic changes. METHODS: Twenty-four male Sprague-Dawley rats were fed either Lieber-DeCarli alcohol diet (36% calories from ethanol) or Lieber-DeCarli control diet along with or without iron supplementation (0...
December 2016: Journal of Cancer Prevention
https://www.readbyqxmd.com/read/28053093/catalytic-determinants-of-alkene-production-by-the-cytochrome-p450-peroxygenase-oletje
#16
Sarah Matthews, James D Belcher, Kang Lan Tee, Hazel M Girvan, Kirsty J McLean, Stephen Ej Rigby, Colin W Levy, David Leys, David A Parker, Richard T Blankley, Andrew W Munro
The Jeotgalicoccus sp. peroxygenase cytochrome P450 OleTJE (CYP152L1) is a hydrogen peroxide-driven oxidase that catalyzes oxidative decarboxylation of fatty acids, producing terminal alkenes with applications as fine chemicals and biofuels. Understanding mechanisms that favor decarboxylation over fatty acid hydroxylation in OleTJE could enable protein engineering to improve catalysis or to introduce decarboxylation activity into P450s with different substrate preferences. In this manuscript, we have focused on OleTJE active site residues Phe79, His85 and Arg245 to interrogate their roles in substrate binding and catalytic activity...
January 4, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28052598/oxygen-atom-transfer-using-an-iron-iv-oxo-embedded-in-a-tetracyclic-n-heterocyclic-carbene-system-how-does-the-reactivity-compare-to-cytochrome-p450-compound
#17
Samuel de Visser, Fabian Cantu Reinhard
N-heterocyclic carbenes (NHC) are common catalyst features in transition metal chemistry. Recently, a cyclic system containing four NHC groups with a central iron atom was synthesized and its iron(IV)-oxo characterized, [FeIV(O)(cNHC4)]2+. This tetra-cyclic NHC ligand system may give the iron(IV)-oxo species unique catalytic properties as compared to traditional nonheme iron and heme iron ligand systems. Therefore, we performed a computational study on the structure and reactivity of the [FeIV(O)(cNHC4)]2+ complex in substrate hydroxylation and epoxidation reactions...
January 4, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28050858/thermophilic-bacteria-are-potential-sources-of-novel-rieske-non-heme-iron-oxygenases
#18
Joydeep Chakraborty, Chiho Suzuki-Minakuchi, Kazunori Okada, Hideaki Nojiri
Rieske non-heme iron oxygenases, which have a Rieske-type [2Fe-2S] cluster and a non-heme catalytic iron center, are an important family of oxidoreductases involved mainly in regio- and stereoselective transformation of a wide array of aromatic hydrocarbons. Though present in all domains of life, the most widely studied Rieske non-heme iron oxygenases are found in mesophilic bacteria. The present study explores the potential for isolating novel Rieske non-heme iron oxygenases from thermophilic sources. Browsing the entire bacterial genome database led to the identification of 45 homologs from thermophilic bacteria distributed mainly among Chloroflexi, Deinococcus-Thermus and Firmicutes...
December 2017: AMB Express
https://www.readbyqxmd.com/read/28049145/the-fumarate-reductase-of-bacteroides-thetaiotaomicron-unlike-that-of-escherichia-coli-is-configured-so-that-it-does-not-generate-reactive-oxygen-species
#19
Zheng Lu, James A Imlay
: The impact of oxidative stress upon organismal fitness is most apparent in the phenomenon of obligate anaerobiosis. The root cause may be multifaceted, but the intracellular generation of reactive oxygen species (ROS) likely plays a key role. ROS are formed when redox enzymes accidentally transfer electrons to oxygen rather than to their physiological substrates. In this study, we confirm that the predominant intestinal anaerobe Bacteroides thetaiotaomicron generates intracellular ROS at a very high rate when it is aerated...
January 3, 2017: MBio
https://www.readbyqxmd.com/read/28045510/anaerobic-heme-degradation-chuy-is-an-anaerobilin-reductase-that-exhibits-kinetic-cooperativity
#20
Joseph W LaMattina, Michael Anthony Delrossi, Katherine Grace Uy, Nicholas D Keul, David B Nix, William Nicholas Lanzilotta
Heme catabolism is an important biochemical process that many bacterial pathogens utilize to acquire iron. However, tetrapyrrole catabolites can be reactive and often require further processing in order for safe transport out of the cell or conversion to another useful cofactor. In previous work, we presented in vitro evidence for an anaerobic heme degradation pathway in Escherichia coli O157:H7. Consistent with reactions that have been reported for other radical SAM methyltransferases, ChuW transfers a methyl group to heme by a radical mediated mechanism and catalyzes the -scission of porphyrin macrocycle...
January 3, 2017: Biochemistry
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