Zeitschriftenartikel: „Catalyseurs – Surfaces“

1

Taoufik, M., C. Santini, JM Basset und JP Candy. „Greffage de dérivés chiraux du germanium sur des surfaces métalliques. Génèse de catalyseurs hétérogènes asymétriques par voie chimie organométallique de surface“. Journal de Chimie Physique 94 (1997): 1969–74. http://dx.doi.org/10.1051/jcp/1997941969.

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2

Zalma, Roger, Lionel Bonneau, Jeanine Fournier, Joëlle Guignard, Françoise Borg und Henri Pezerat. „Hydrodésazotation de l'indole sur catalyseur fer supporté sur amiante“. Canadian Journal of Chemistry 65, Nr. 3 (01.03.1987): 523–27. http://dx.doi.org/10.1139/v87-091.

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The aim of this study is to examine hydrodenitrogenation (HDN) of indole on asbestos catalysts (chrysotile and crocidolite) under hydrogen pressure. HDN is carried out according to two competitive pathways, either via ortho-ethylaniline or via ortho-toluidine. This reaction is assisted by increase of temperature and pressure and by pre-reduction of the asbestos. Particles of Fe0on the fibre surface are formed from the original material. Their presence plays a role in the initial breaking of the C—N bond and in the hydrogenation reaction.

3

Schneider, E. M., M. Zeltner, N. Kränzlin, R. N. Grass und W. J. Stark. „Base-free Knoevenagel condensation catalyzed by copper metal surfaces“. Chemical Communications 51, Nr. 53 (2015): 10695–98. http://dx.doi.org/10.1039/c5cc02541a.

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4

Alonso, Rafael, Pilar Jiménez-Meneses, Jaime García-Rupérez, María-José Bañuls und Ángel Maquieira. „Thiol–ene click chemistry towards easy microarraying of half-antibodies“. Chemical Communications 54, Nr. 48 (2018): 6144–47. http://dx.doi.org/10.1039/c8cc01369a.

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5

Weiss, Karin, und Kurt Hoffmann. „Untersuchungen von Polymerisations-und Metathesereaktionen, X. Mitt. [1] Polymerisation, Trimerisation und Metathese von Allenen und Heteroallenen mit reduziertem Phillips-Katalysator / Studies of Polymerisation and Metathesis Reactions, Part X [1] Polymerisation, Trimerisation and Metathesis of Allenes and Heteroallenes with Reduced Phillips Catalyst“. Zeitschrift für Naturforschung B 42, Nr. 6 (01.06.1987): 769–73. http://dx.doi.org/10.1515/znb-1987-0621.

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Abstract The reduced Phillips Catalyst - a surface chromium(II) on silica - catalyses the polymerisation of the allene 1,2-butadiene to yield predominantly 1,2-polybutadiene, yields trimerisation products with isocyanates, and gives metathesis of 2 differently substituted carbodiimides.

6

Fukui, Ken-ichi, Satoru Takakusagi, Ryugo Tero, Masaki Aizawa, Yoshimichi Namai und Yasuhiro Iwasawa. „Dynamic aspects and associated structures of TiO2(110) and CeO2(111) surfaces relevant to oxide catalyses“. Physical Chemistry Chemical Physics 5, Nr. 24 (2003): 5349. http://dx.doi.org/10.1039/b307879e.

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7

Yang, Bin, Jianping Li, Lianming Zhang und Guobao Xu. „A molecularly imprinted electrochemiluminescence sensor based on the mimetic enzyme catalytic effect for ultra-trace Ni2+ determination“. Analyst 141, Nr. 20 (2016): 5822–28. http://dx.doi.org/10.1039/c6an00926c.

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The complex of Ni-DMG acts as the template molecule modified on the MIP electrode surface. As a mimetic enzyme, it catalyses the oxidation of luminol to enhance the ECL signal. The ECL intensities produced by the luminol-H₂O₂ ECL system provide the basis for Ni²⁺ determination.

8

Liu, Jian, Fei He und Ka Di Zhu. „Surface plasmonic catalysis based on molecular optomechanics“. Europhysics Letters 137, Nr. 2 (01.01.2022): 25002. http://dx.doi.org/10.1209/0295-5075/ac4d3f.

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Abstract Nowadays, researchers find that the surface plasmons can mediate some chemical reactions through the generation of the confined plasmonic field, excited electrons, and local heating effect. In this article we suggest a new surface plasmonic photocatalysis mechanism based on the molecular optomechanics which is not considered before. A reaction kinetic model was established to achieve a quantitative study of catalytic efficiency. The catalytic mechanism is not limited to a specific chemical reaction, all molecules with Raman activity can be accelerated dramatically in reaction. For molecules with different mechanical properties, the corresponding optomechanical catalytic pathway needs to be selected. We hope that this work will provide guidance for achieving strong or even ultrastrong catalyses under specific optical conditions. We further demonstrate that the optomechanical effects can also be used for the deceleration, which provides the possibility to design a highly tunable chemical reaction system. We believe that the quantum photochemistry will be further developed and widely used in future research.

9

Paille, Grégoire, Amandine Boulmier, Alexandre Bensaid, Minh-Huong Ha-Thi, Thu-Trang Tran, Thomas Pino, Jérôme Marrot et al. „An unprecedented {Ni14SiW9} hybrid polyoxometalate with high photocatalytic hydrogen evolution activity“. Chemical Communications 55, Nr. 29 (2019): 4166–69. http://dx.doi.org/10.1039/c9cc01269a.

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10

Pattanaik, Sandip, und Chidambaram Gunanathan. „Cobalt-catalysed selective synthesis of aldehydes and alcohols from esters“. Chemical Communications 56, Nr. 53 (2020): 7345–48. http://dx.doi.org/10.1039/d0cc03076g.

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11

Ma, Guo Feng, Hong Ling Zhang und Xue Fei Yang. „Formation of a Low Reflective Surface on Silicon Solar Cells by Chemical Treatment Using Ag-Assisted Electroless Etching“. Advanced Materials Research 512-515 (Mai 2012): 43–46. http://dx.doi.org/10.4028/www.scientific.net/amr.512-515.43.

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The Ag-assisted electroless etching of p-type silicon substrate in HF/H2O2solution at room temperature was investigated. The porous silicon layer was formed in a mixed solution of H2O2and HF by using screen-printed Ag front electrodes as the catalyst. And influence of the different concentration etching solution (HF and AgNO3) on the porous silicon layer was study by scanning electron microscopy (SEM). Through investigation of the track of catalyst particles, it was shown that Ag really catalyses the etching of silicon underneath Ag particle.

12

Yang, Haiyan, Wenxing Lv, Ming He, Haiteng Deng, Haitao Li, Wei Wu und Yu Rao. „Plasticity in designing PROTACs for selective and potent degradation of HDAC6“. Chemical Communications 55, Nr. 98 (2019): 14848–51. http://dx.doi.org/10.1039/c9cc08509b.

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13

Shylin, Sergii I., Mariia V. Pavliuk, Luca D’Amario, Fikret Mamedov, Jacinto Sá, Gustav Berggren und Igor O. Fritsky. „Efficient visible light-driven water oxidation catalysed by an iron(iv) clathrochelate complex“. Chemical Communications 55, Nr. 23 (2019): 3335–38. http://dx.doi.org/10.1039/c9cc00229d.

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14

Zhao, Yunbo, Lvnan Jin, Jing Guo und Douglas W. Stephan. „Catalytic hydroaminations of alkynes: a facile protocol to vinyl-carbazole derivatives via a frustrated Lewis pair mechanism“. Chemical Communications 58, Nr. 18 (2022): 3039–42. http://dx.doi.org/10.1039/d1cc07171h.

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15

Arto, Tamara, Patricia Fernández, Francisco J. Fañanás und Félix Rodríguez. „Complex chromene derivatives through a silver-catalysed cascade reaction of simple o-alkynylsalicylaldehydes and alkenes“. Chemical Communications 52, Nr. 91 (2016): 13405–8. http://dx.doi.org/10.1039/c6cc07801j.

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Silver triflate catalyses a complex transformation of simple ortho-alkynylsalicylaldehydes and alkenes to give benzo[de]chromenyl ketones in a process that involves two formal [4+2]-cyclization reactions.

16

Déziel, Eric, François Lépine, Sylvain Milot und Richard Villemur. „rhlA is required for the production of a novel biosurfactant promoting swarming motility in Pseudomonas aeruginosa: 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs), the precursors of rhamnolipids“. Microbiology 149, Nr. 8 (01.08.2003): 2005–13. http://dx.doi.org/10.1099/mic.0.26154-0.

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Pseudomonas aeruginosa produces extracellular glycolipids composed of l-rhamnose and 3-hydroxyalkanoic acid called rhamnolipids. Although these compounds are usually regarded as biosurfactants or haemolysins, their exact physiological function is not well understood. Rhamnolipids are synthesized by a rhamnosyltransferase, encoded by the rhlAB operon, which catalyses the transfer of TDP-l-rhamnose to 3-(3-hydroxyalkanoyloxy)alkanoic acid (HAA) moieties of various lengths. RhlB is the catalytic protein of the rhamnosyltransferase. rhlA is indispensable for rhamnolipid synthesis, but its function is unknown. Using a liquid chromatography/mass spectrometry method, the production of extracellular HAAs by P. aeruginosa was detected previously and it was demonstrated that they are the actual precursors of rhamnolipid biosynthesis. In this report, evidence is presented indicating that rhlA is required for production of HAAs and that these HAAs display potent surface-active properties. P. aeruginosa can colonize surfaces by swarming motility, a form of organized translocation requiring the production of wetting agents. Using rhlA and rhlB mutants it was observed that swarming requires the expression of the rhlA gene but does not necessitate rhamnolipid production, as HAAs act as surfactants. Finally, it was shown that the use of ammonium instead of nitrate as source of nitrogen and an excess of available iron both decrease rhlA expression and swarming motility.

17

Guerrero Fajardo, Carlos Alberto, Yvonne N’Guyen, Claire Courson und Anne Cécile Roger. „Fe/SiO2 catalysts for the selective oxidation of methane to formaldehyde“. Ingeniería e Investigación 26, Nr. 2 (01.05.2006): 37–44. http://dx.doi.org/10.15446/ing.investig.v26n2.14735.

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Selective oxidation of methane to formaldehyde was analysed with iron catalysts supported on silica prepared by the sol-gel method, leading to obtaining a large support surface area facilitating high dispersion of iron on silica’s amorphous surface. Seven catalysts were prepared; one of them corresponded to the silica support and another five having an iron load 0.1-0.5% in weight. Catalyst 7 (0.5% Fe in weight) was prepared with neutral pH control and had the most homogeneous characteristics since it did not present isolated iron species, corroborated by SEM and TEM analysis. The highest BET areas were 1,757 and 993 m2.g-1 for 0.5% Fe catalysts, having an average 36% microporosity and 43% mesoporosity. X-ray diffraction confirmed the catalyst’s amorphous structure. Catalytic activity was carried out with catalyser 7 at atmospheric pressure in a quartz reactor using a CH4/O2/N2=7.5/1/4 reaction mixture at 400-750°C temperature range. Reaction products were analysed by gas chromatography with TCD. The heterogeneous catalysts displayed greater methane conversion (but with methanol selectivity) whereas homogenous catalyst 7 gave better results regarding formaldehyde. The highest conversion percentage (8.60% mol) for catalyser 7 was presented at 650°C. Formaldehyde selectivity was 50% mol in the 600-650°C range and maximum yield (0.31g HCHO/Kg catalyst) was found in this range; it was thus considered that 650°C for the reaction was thereby the best operating temperature.

18

Pandey, Pragati, und Jitendra K. Bera. „Hydrosilylative reduction of primary amides to primary amines catalyzed by a terminal [Ni–OH] complex“. Chemical Communications 57, Nr. 73 (2021): 9204–7. http://dx.doi.org/10.1039/d1cc03537a.

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A terminal [Ni–OH] complex, stabilized by triflamide-tethered NHC ligands, selectively catalyses the deoxygenative reduction of primary amides to primary amines using phenylsilane as the reductant, without proceeding via a nitrile intermediate.

19

Zhou, Shanshan, Nicolas R. Malet, Lijiang Song, Christophe Corre und Gregory L. Challis. „MmfL catalyses formation of a phosphorylated butenolide intermediate in methylenomycin furan biosynthesis“. Chemical Communications 56, Nr. 92 (2020): 14443–46. http://dx.doi.org/10.1039/d0cc05658h.

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MmfL forms phosphorylated butenolides that undergo dephosphorylation and rearrangement to yield methylenomycin furan (MMF) signalling molecules that induce antibiotic production in Streptomyces coelicolor.

20

Sato, Yoshinori, Yuushou Nakayama und Hajime Yasuda. „Synthesis of pentavalent imidovanadium complexes and their catalyses for the polymerization of ethylene and propylene“. Journal of Applied Polymer Science 97, Nr. 3 (2005): 1008–15. http://dx.doi.org/10.1002/app.21826.

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21

Wang, Ching-Shuen, Huaizhong Pan, G. Mahika Weerasekare und Russell J. Stewart. „Peroxidase-catalysed interfacial adhesion of aquatic caddisworm silk“. Journal of The Royal Society Interface 12, Nr. 112 (November 2015): 20150710. http://dx.doi.org/10.1098/rsif.2015.0710.

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Casemaker caddisfly ( Hesperophylax occidentalis ) larvae use adhesive silk fibres to construct protective shelters under water. The silk comprises a distinct peripheral coating on a viscoelastic fibre core. Caddisworm silk peroxinectin (csPxt), a haem-peroxidase, was shown to be glycosylated by lectin affinity chromatography and tandem mass spectrometry. Using high-resolution H 2 O 2 and peroxidase-dependent silver ion reduction and nanoparticle deposition, imaged by electron microscopy, csPxt activity was shown to be localized in the peripheral layer of drawn silk fibres. CsPxt catalyses dityrosine cross-linking within the adhesive peripheral layer post-draw, initiated perhaps by H 2 O 2 generated by a silk gland-specific superoxide dismutase 3 (csSOD3) from environmental reactive oxygen species present in natural water. CsSOD3 was also shown to be a glycoprotein and is likely localized in the peripheral layer. Using a synthetic fluorescent phenolic copolymer and confocal microscopy, it was shown that csPxt catalyses oxidative cross-linking to external polyphenolic compounds capable of diffusive interpenetration into the fuzzy peripheral coating, including humic acid, a natural surface-active polyphenol. The results provide evidence of enzyme-mediated covalent cross-linking of a natural bioadhesive to polyphenol conditioned interfaces as a mechanism of permanent adhesion underwater.

22

Perdigones, Nieves, Mariela Morales, Philip Mason und Monica Bessler. „Case Report: Paroxysmal nocturnal hemoglobinuria in a woman heterozygous for G6PD A-“. F1000Research 3 (21.10.2014): 194. http://dx.doi.org/10.12688/f1000research.4980.2.

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We describe a case of paroxysmal nocturnal hemoglobinuria (PNH) in a woman who is heterozygous for the glucose-6-phosphate dehydrogenase A- (G6PDA-) allele. PNH is associated with one or more clones of cells that lack complement inhibition due to loss of function somatic mutations in thePIGAgene. PIGAencodes the enzyme phosphatidylinositol glycan anchor biosynthesis, class A, which catalyses the first step of glycosylphosphatidylinisotol (GPI) anchor synthesis. Two GPI anchored red cell surface antigens regulate complement lysis. G6PD catalyses the first step of the pentose phosphate pathway and enzyme variants, frequent in some populations have been selected because they confer resistance to malaria, are associated with hemolysis in the presence of oxidizing agents including several drugs. The patient had suffered a hemolytic attack after taking co-trimoxazole, a drug that precipitates hemolysis in G6PD deficient individuals. Since bothG6PDandPIGAare X-linked we hypothesized that thePIGAmutation was on the X-chromosome carrying theG6PDA- allele. Investigations showed that in fact thePIGAmutation was on the X-chromosome carrying the normalG6PD Ballele. We speculate that complement activation onG6PD A- red cells exposed to Bactrim might have triggered complement activation inducing the lysis ofG6PD BPNH Type II red blood cells or that the patient may have had a PNH clone expressingG6PDA-at the time of the hemolytic episode.

23

Geissler, Heidrun, Ronald Ullmann und Thierry Soldati. „The Tail Domain of Myosin M Catalyses Nucleotide Exchange on Rac1 GTPases and Can Induce Actin-Driven Surface Protrusions“. Traffic 1, Nr. 5 (Mai 2000): 399–410. http://dx.doi.org/10.1034/j.1600-0854.2000.010505.x.

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24

Zheng, Jun, Mingyan Wu, Feilong Jiang, Weiping Su und Maochun Hong. „Stable porphyrin Zr and Hf metal–organic frameworks featuring 2.5 nm cages: high surface areas, SCSC transformations and catalyses“. Chemical Science 6, Nr. 6 (2015): 3466–70. http://dx.doi.org/10.1039/c5sc00213c.

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25

ANDERSON, Peter J. „A dimeric form of prothrombin on membrane surfaces“. Biochemical Journal 336, Nr. 3 (15.12.1998): 631–38. http://dx.doi.org/10.1042/bj3360631.

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Blood coagulation requires the conversion of zymogens to active enzymes. These reactions are facilitated by Ca2+-dependent protein binding to membrane surfaces containing anionic phospholipids. Here it is shown that only in the presence of both Ca2+ and phospholipid vesicles composed of phosphatidylcholine and phosphatidylserine can a prothrombin dimer be chemically cross-linked. A cross-linker containing evenly spaced reactive groups was prepared by activating the carboxy groups of a ten-residue glutamic acid peptide and allowed to react with physiological concentrations of prothrombin. When Ca2+ and anionic phospholipids were both present during exposure to the cross-linker, it was found that more than 50% of the prothrombin was trapped as a chemically defined dimer with reaction times of the order of 1 min. The dimer yield remained high even when reactions were performed at high phospholipid-to-protein ratios at protein concentrations an order of magnitude less than physiological. Amino acid sequencing of a CNBr peptide produced from the purified dimer localized the cross-link to residues Lys341 and Lys427 of prothrombin. The specificity and high yield under mild conditions of the cross-linking suggest that dimeric membrane bound prothrombin might be a physiologically relevant substrate for the formation of thrombin. Prothrombinase converts this modified protein to an enzyme that catalyses the hydrolysis of a thrombin chromogenic substrate as efficiently as thrombin and is inhibited by a thrombin active-site directed inhibitor, but is a thrombin dimer. The thrombin dimer has impaired activity compared with thrombin with respect to physiological functions requiring binding to exosite I. A model based on the known structure of thrombin is presented that can account for the prothrombin dimer and the properties of the dimeric thrombin formed from it.

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Phillips, Robert S., und Louis A. Cohen. „Intramolecular general acid and general base catalyses in the hydrolysis of 2-halotryptophans and their analogs“. Journal of the American Chemical Society 108, Nr. 8 (April 1986): 2023–30. http://dx.doi.org/10.1021/ja00268a049.

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27

ROOT, Paul, Inga SLISKOVIC und Bulent MUTUS. „Platelet cell-surface protein disulphide-isomerase mediated S-nitrosoglutathione consumption“. Biochemical Journal 382, Nr. 2 (24.08.2004): 575–80. http://dx.doi.org/10.1042/bj20040759.

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S-nitrosothiols (RSNOs) regulate several aspects of platelet physiology including inhibition of activation, adhesion and aggregation. PDI (protein disulphide-isomerase) has recently been found to be localized to the cell surface, where it exhibits both disulphide-exchange and denitrosation activities. The disulphide-exchange activity of PDI has been linked to aspects of platelet aggregation. The present study suggests that the metabolism of RSNOs by platelets is a function of PDI denitrosation activity. Exposure of washed human platelets to increasing concentrations of GSNO (S-nitrosoglutathione) resulted in saturable denitrosation kinetics. The presence of known PDI inhibitors phenylarsine oxide and anti-PDI antibodies prevented GSNO denitrosation. The fact that, in the presence of GSNO plus the cell-permeable guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxaline-1-one, the initial rates of ADP-induced platelet aggregation and the maximum ΔOD were diminished by ∼40% shows that RSNOs have dual inhibitory effects on platelets, which are mediated through PDI. First, PDI denitrosates RSNOs, releasing NO that, via the guanylate cyclase/G-kinase route, attenuates platelet activation. Secondly, RSNOs are denitrosated at the same PDI-active site that catalyses the disulphide bond formation between integrins and their ligands, thereby attenuating irreversible aggregation.

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Delannay, F., E. N. Haeussler und B. Delmon. „Étude Par Spectrométrie De Diffusion Ionique De La Structure De La Bi-Couche D'Oxyde De Molybdene Et De Cobalt A La Surface Du Support Des Catalyseurs D'Hydrodésulfuration“. Bulletin des Sociétés Chimiques Belges 89, Nr. 4 (01.09.2010): 255–59. http://dx.doi.org/10.1002/bscb.19800890401.

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29

Perdigones, Nieves, Mariela Morales, Philip Mason und Monica Bessler. „Case Report: Paroxysmal nocturnal hemoglobinuria in a woman heterozygous for G6PD A-“. F1000Research 3 (13.08.2014): 194. http://dx.doi.org/10.12688/f1000research.4980.1.

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We describe a case of paroxysmal nocturnal hemoglobinuria (PNH) in a woman who is heterozygous for the glucose-6-phosphate dehydrogenase A- (G6PDA-) allele. PNH is associated with one or more clones of cells that lack complement inhibition due to loss of function somatic mutations in thePIGAgene. PIGAencodes the enzyme phosphatidylinositol glycan anchor biosynthesis, class A, which catalyses the first step of glycosylphosphatidylinisotol (GPI) anchor synthesis. Two GPI anchored red cell surface antigens regulate complement lysis. G6PD catalyses the first step of the pentose phosphate pathway and enzyme variants, frequent in some populations have been because they confer resistance to malaria, are associated with hemolysis in the presence of oxidizing agents including several drugs. The patient had suffered a hemolytic attack after taking Bactrim, a drug that precipitates hemolysis in G6PD deficient individuals. Since bothG6PDandPIGAare X-linked we hypothesized that the PIGA mutation was on the X-chromosome carrying the G6PDA- allele. Investigations showed that in fact the PIGA mutation was on the X-chromosome carrying the normalG6PD Ballele. We speculate that complement activation on G6PD A- red cells exposed to Bactrim might have triggered complement activation inducing the lysis of G6PD B PNH Type II red blood cells or that the patient may have had a PNH clone expressing G6PDA- at the time of the hemolytic episode.

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Jiang, Yijun, und Qiuming Gao. „Heterogeneous Hydrogenation Catalyses over Recyclable Pd(0) Nanoparticle Catalysts Stabilized by PAMAM-SBA-15 Organic−Inorganic Hybrid Composites“. Journal of the American Chemical Society 128, Nr. 3 (Januar 2006): 716–17. http://dx.doi.org/10.1021/ja056424g.

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31

Males, Alexandra, und Gideon J. Davies. „Structural studies of a surface-entropy reduction mutant of O-GlcNAcase“. Acta Crystallographica Section D Structural Biology 75, Nr. 1 (01.01.2019): 70–78. http://dx.doi.org/10.1107/s2059798318016595.

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The enzyme O-GlcNAcase catalyses the removal of the O-GlcNAc co/post-translational modification in multicellular eukaryotes. The enzyme has become of acute interest given the intimate role of O-GlcNAcylation in tau modification and stability; small-molecular inhibitors of human O-GlcNAcase are under clinical assessment for the treatment of tauopathies. Given the importance of structure-based and mechanism-based inhibitor design for O-GlcNAcase, it was sought to test whether different crystal forms of the human enzyme could be achieved by surface mutagenesis. Guided by surface-entropy reduction, a Glu602Ala/Glu605Ala variant [on the Gly11–Gln396/Lys535–Tyr715 construct; Roth et al. (2017), Nature Chem. Biol. 13, 610–612] was obtained which led to a new crystal form of the human enzyme. An increase in crystal contacts stabilized disordered regions of the protein, enabling 88% of the structure to be modelled; only 83% was possible for the wild-type construct. Although the binding of the C-terminus was consistent with the wild type, Lys713 in monomer A was bound in the −1 subsite of the symmetry-related monomer A and the active sites of the B monomers were vacant. The new crystal form presents an opportunity for enhanced soaking experiments that are essential to understanding the binding mechanism and substrate specificity of O-GlcNAcase.

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Jaafar, Nardiah Rizwana, Dene Littler, Travis Beddoe, Jamie Rossjohn, Rosli Md Illias, Nor Muhammad Mahadi, Mukram Mohamed Mackeen, Abdul Munir Abdul Murad und Farah Diba Abu Bakar. „Crystal structure of fuculose aldolase from the Antarctic psychrophilic yeastGlaciozyma antarcticaPI12“. Acta Crystallographica Section F Structural Biology Communications 72, Nr. 11 (27.10.2016): 831–39. http://dx.doi.org/10.1107/s2053230x16015612.

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Fuculose-1-phosphate aldolase (FucA) catalyses the reversible cleavage of L-fuculose 1-phosphate to dihydroxyacetone phosphate (DHAP) and L-lactaldehyde. This enzyme from mesophiles and thermophiles has been extensively studied; however, there is no report on this enzyme from a psychrophile. In this study, the gene encoding FucA fromGlaciozyma antarcticaPI12 (GaFucA) was cloned and the enzyme was overexpressed inEscherichia coli, purified and crystallized. The tetrameric structure of GaFucA was determined to 1.34 Å resolution. The overall architecture of GaFucA and its catalytically essential histidine triad are highly conserved among other fuculose aldolases. Comparisons of structural features between GaFucA and its mesophilic and thermophilic homologues revealed that the enzyme has typical psychrophilic attributes, indicated by the presence of a high number of nonpolar residues at the surface and a lower number of arginine residues.

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Price, H. P., D. Goulding und D. F. Smith. „ARL1 has an essential role in Trypanosoma brucei“. Biochemical Society Transactions 33, Nr. 4 (01.08.2005): 643–45. http://dx.doi.org/10.1042/bst0330643.

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Myristoyl-CoA protein:NMT (N-myristoyl transferase) catalyses the N-myristoylation of cellular proteins with a range of functions and is essential for viability in the protozoan parasites, Leishmania major and Trypanosoma brucei. In our investigations to define the essential downstream targets of NMT, we have focused on the ARF (ADP-ribosylation factor) family of proteins, as growth arrest in Saccharomyces cerevisiae mutants with reduced NMT activity correlates with decreased modification of members of this group of proteins. We have identified nine ARF/ARLs (where ARL stands for ARF-like) encoded in the T. brucei and T. cruzi genomes and ten in L. major. The T. brucei ARL1 protein is expressed only in the mammalian bloodstream form of the parasite, in which it is localized to the Golgi apparatus. RNAi (RNA interference) has been used to demonstrate that ARL1 is essential for viability in these infective cells. Before cell death, depletion of ARL1 protein results in disintegration of the Golgi structure and a delay in exocytosis of the abundant GPI (glycosylphosphatidylinositol)-anchored VSG (variant surface glycoprotein) to the parasite surface.

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Waters, Tom, George N. Khairallah, Samantha A. S. Y. Wimala, Yien C. Ang, Richard A. J. O'Hair und Anthony G. Wedd. „Mononuclear metavanadate catalyses gas phase oxidation of methanol to formaldehyde employing dioxygen as the terminal oxidant“. Chemical Communications, Nr. 43 (2006): 4503. http://dx.doi.org/10.1039/b612384h.

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Horino, Atsuko, Tsuyoshi Kenri, Yuko Sasaki, Noboru Okamura und Tsuguo Sasaki. „Identification of a site-specific tyrosine recombinase that mediates promoter inversions of phase-variable mpl lipoprotein genes in Mycoplasma penetrans“. Microbiology 155, Nr. 4 (01.04.2009): 1241–49. http://dx.doi.org/10.1099/mic.0.025437-0.

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Mycoplasma penetrans has the ability to change its surface lipoprotein profiles frequently. The P35 family lipoproteins encoded by the mpl genes are key players in this profile variation. The M. penetrans HF-2 genome has 38 mpl genes that form three gene clusters. Most of these mpl genes have an invertible promoter sequence that is responsible for the ON/OFF switching of individual mpl gene expression. Here, we identified the recombinase that catalyses inversions of the mpl gene promoters. We focused on two open reading frames of the M. penetrans HF-2 genome, namely MYPE2900 and MYPE8180, which show significant homology to the tyrosine site-specific recombinase (Tsr) family proteins. Since genetic tools for M. penetrans are still not developed, we cloned the MYPE2900 and MYPE8180 genes and expressed them in Mycoplasma pneumoniae and Escherichia coli. The promoter regions of the mpl genes [p35 (MYPE6810) or p42 (MYPE6630) genes] were also introduced into M. pneumoniae and E. coli cells expressing MYPE2900 or MYPE8180. Inversion of these promoters occurred in the presence of the MYPE2900 gene but not in the presence of the MYPE8180 gene, indicating that the MYPE2900 gene product is the recombinase that catalyses mpl gene promoter inversions. We used a PCR-based method to detect mpl promoter inversion. This method also enabled us to detect inversions of 10 mpl gene promoters in M. penetrans HF-2 cells. All these promoter inversions occurred at the 12 bp inverted repeat (IR) sequences flanking the promoter sequence. The consensus sequence of these IRs was proposed as TAAYNNNDATTA (Y=C or T; D=A, G or T).

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Merabet, Smail, Abdelkrim Bouzaza, Mohamed Bouhelassa und Dominique Wolbert. „Modélisation et optimisation de la photodégradation du 4-méthylphénol dans un réacteur à recirculation en présence d’UV/ZnO“. Revue des sciences de l'eau 22, Nr. 4 (22.10.2009): 565–73. http://dx.doi.org/10.7202/038331ar.

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Résumé L’étude de la photodégradation du 4-méthylphénol a été menée sur un pilote à recirculation. Cette molécule a été prise comme composé modèle pour le traitement des effluents de l’industrie avicole. Ce travail a consisté en l’optimisation et la modélisation de l’élimination du 4-méthylphénol par photocatalyse en présence de ZnO. L’utilisation des plans d’expériences, et en particulier de la méthodologie de surface de réponse (RSM) et un plan central composite (CCD), a permis la détermination de l’influence des effets simultanés et de l’interaction des paramètres opératoires sur le rendement de la photodégradation. Les paramètres étudiés sont la concentration initiale en 4-méthylphénol, la concentration en catalyseur et le débit de recirculation de la solution. Les résultats montrent que l’application de la RSM permet de décrire d’une manière correcte l’influence de ces trois paramètres expérimentaux sur l’efficacité du traitement. Les valeurs optimales des paramètres donnant un rendement maximal (100 %) ont pu être déterminées. Les modèles de second ordre obtenus, pour le rendement de dégradation et pour l’abattement de DCO, ont été validés en utilisant différentes approches statistiques. L’utilisation de la méthode ANOVA a montré que les modèles sont hautement significatifs et en bonne adéquation avec les résultats expérimentaux.

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Amaya, Jeceny, Andrés Tristancho und Francisco José Sánchez Castellanos. „Employing fly ash and FCC catalyzer waste in recovering chrome (III) from liquid effluent emitted by tanneries“. Ingeniería e Investigación 25, Nr. 1 (01.01.2005): 39–48. http://dx.doi.org/10.15446/ing.investig.v25n1.14619.

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The present work studies the possibility of using two solid industrial wastes TERMOPAIPA'S fly ash and ECOPETROUS FCC catalyzer waste in removing and recovering chrome from tanneries’ liquid effluent. Fly ash was subjected to two alkaline hydrothermal treatments for obtaining zeolytic structures having better properties; waste catalyser was calcined for eliminating surface coke. Solids were characterized following treatment including DRX, BET area and CEC. A colorimetric method was standardized for determining chrome in solution; a response surface experimental design was implemented for finding optimum removal conditions. The most efficient adsorbent was fly ash treated with increased NaOH concentration; optimum conditions for removing chrome were: 58 minutes at 36°C, 5.9 pH and 31% w/v solid removal. When reused, it was found that the two batches of treated fly ash became saturated following 6 cycles of use, whilst original ash and FCC catalyzer became saturated the second time they were used. Four de-absorbent agents were used for recovering chrome from adsorbent product, H2SO4 0.6 M being the best. Field trials showed that removal efficiency became reduced by the effect of other contaminants, depending on the solution’s initial concentration.

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REBECCHI, Mario, Marjorie BONHOMME und Suzanne SCARLATA. „Role of lipid packing in the activity of phospholipase C-δ1 as determined by hydrostatic pressure measurements“. Biochemical Journal 341, Nr. 3 (26.07.1999): 571–76. http://dx.doi.org/10.1042/bj3410571.

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Previous studies with phospholipid monolayers revealed a large decrease in the activity of phosphoinositide-specific phospholipase C-δ1 (PLC-δ1) which catalyses the hydrolysis of PtdIns(4,5)P2 as lateral pressure is applied to the membrane. If stress on the membrane is the sole inhibitor of PLC-δ1 activity, the enzyme must penetrate the membrane surface to engage its substrate. To test the effect on PLC-δ1 activity of lipid packing in the absence of a directional stress, we examined the effects of increasing hydrostatic pressure on enzymic activity. We find that, in contrast with monolayer studies, increasing lipid packing by hydrostatic pressure does not affect membrane binding and increases enzymic activity by 90% in going from atmospheric pressure to 108 Pa (approx. 1000 atm). The increase in activity could be accounted for mainly by electrostriction of water around the multiply-charged product. Our results show that when there is no net stress on the monolayer, lipid packing does not alter PLC-δ1 activity, possibly because penetration of the enzyme into the membrane surface is shallow. We suggest that, in biological membranes, the activity of this and possibly other interfacial proteins is independent of headgroup packing.

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Barazorda-Ccahuana, Haruna L., Badhin Gómez, Francesc Mas und Sergio Madurga. „Effect of pH on the Supramolecular Structure of Helicobacter pylori Urease by Molecular Dynamics Simulations“. Polymers 12, Nr. 11 (17.11.2020): 2713. http://dx.doi.org/10.3390/polym12112713.

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The effect of pH on the supramolecular structure of Helicobacter pylori urease was studied by means of molecular dynamics simulations at seven different pHs. Appropriate urease charge distributions were calculated using a semi-grand canonical Monte Carlo (SGCMC) procedure that assigns each residue’s charge state depending on the assigned individual pKa obtained by PROPKA. The effect of pH on protein stability has been analyzed through root-mean-square deviation (RMSD), radius of gyration (RG), solvent-accessible surface area (SASA), hydrogen bonds (HB) and salt bridges (SB). Urease catalyses the hydrolysis of urea in 12 active sites that are covered by mobile regions that act like flaps. The mobility of these flaps is increased at acidic pHs. However, extreme acidic conditions cause urease to have the least number of stabilizing interactions. This initiates the process of denaturalization, wherein the four (αβ)3 subunits of the global structure ((αβ)3)4 of urease start to separate.

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Nath, Ipsita, Jeet Chakraborty, Sara Abednatanzi und Pascal Van Der Voort. „A ‘Defective’ Conjugated Porous Poly-Azo as Dual Photocatalyst“. Catalysts 11, Nr. 9 (31.08.2021): 1064. http://dx.doi.org/10.3390/catal11091064.

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A heterogeneous photocatalyst amenable to catalyze different chemical reactions is a highly enabling and sustainable material for organic synthesis. Herein we report the synthesis and characterization of an azobenzene-based organic π–conjugated porous polymer (AzoCPP) as heterogeneous dual photocatalyst manifesting net-oxidative bromination of arenes and dehydroxylation of boronic acids to corresponding phenols. Hierarchical porosity and high surface area of the nano-sized AzoCPP allowed superior catalyst-substrate contact during catalyses, whereas the inherent structural defect present in the CPP backbone resulted in low-energy sinks functioning as de facto catalytic sites. A combination of these two structure-property aspects of AzoCPP, in addition to the dielectric constant manipulation of the system, led to excellent catalytic performance. The protocols remained valid for a wide substrate scope and the catalyst was recycled multiple times without substantial loss in catalytic activity. With the aid of subsequent control experiments and analytical characterizations, mechanisms for each catalysis are proposed and duly corroborated.

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Lia, Andrea, Adam Dowle, Chris Taylor, Angelo Santino und Pietro Roversi. „Partial catalytic Cys oxidation of human GAPDH“. Wellcome Open Research 5 (01.06.2020): 114. http://dx.doi.org/10.12688/wellcomeopenres.15893.1.

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Background: n-Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyses the reversible NAD+-dependent oxidative phosphorylation of n-glyceraldehyde-3-phosphate to 1,3-diphospho-n-glycerate in both glycolysis and gluconeogenesis. Methods: Four distinct crystal structures of human n-Glyceraldehyde-3-phosphate dehydrogenase (HsGAPDH) have been determined from protein purified from the supernatant of HEK293F human epithelial kidney cells. Results: X-ray crystallography and mass-spectrometry indicate that the catalytic cysteine of the protein (HsGAPDH Cys152) is partially oxidised to cysteine S-sulfonic acid. The average occupancy for the Cys152-S-sulfonic acid modification over the 20 crystallographically independent copies of HsGAPDH across three of the crystal forms obtained is 0.31±0.17. Conclusions: The modification induces no significant structural changes on the tetrameric enzyme, and only makes aspecific contacts to surface residues in the active site, in keeping with the hypothesis that the oxidising conditions of the secreted mammalian cell expression system result in HsGAPDH catalytic cysteine S-sulfonic acid modification and irreversible inactivation of the enzyme.

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Lia, Andrea, Adam Dowle, Chris Taylor, Angelo Santino und Pietro Roversi. „Partial catalytic Cys oxidation of human GAPDH to Cys-sulfonic acid.“ Wellcome Open Research 5 (25.08.2020): 114. http://dx.doi.org/10.12688/wellcomeopenres.15893.2.

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Background: n-Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyses the NAD+-dependent oxidative phosphorylation of n-glyceraldehyde-3-phosphate to 1,3-diphospho-n-glycerate and its reverse reaction in glycolysis and gluconeogenesis. Methods: Four distinct crystal structures of human n-Glyceraldehyde-3-phosphate dehydrogenase (HsGAPDH) have been determined from protein purified from the supernatant of HEK293F human epithelial kidney cells. Results: X-ray crystallography and mass-spectrometry indicate that the catalytic cysteine of the protein (HsGAPDH Cys152) is partially oxidised to cysteine S-sulfonic acid. The average occupancy for the Cys152-S-sulfonic acid modification over the 20 crystallographically independent copies of HsGAPDH across three of the crystal forms obtained is 0.31±0.17. Conclusions: The modification induces no significant structural changes on the tetrameric enzyme, and only makes aspecific contacts to surface residues in the active site, in keeping with the hypothesis that the oxidising conditions of the secreted mammalian cell expression system result in HsGAPDH catalytic cysteine S-sulfonic acid modification and irreversible inactivation of the enzyme.

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Livesley, M. A., N. J. Bulleid und C. M. Bray. „Protein disulfide isomerase in germinating wheat (Triticum aestivum) seed and during loss of viability“. Seed Science Research 2, Nr. 2 (Juni 1992): 97–103. http://dx.doi.org/10.1017/s0960258500001197.

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AbstractProtein disulfide isomerase (PDI E.C. 5.3.4.1) catalyses the formation of disulfide bonds in secretory or cell-surface proteins during their biosynthesis. PDI activity is associated with the microsomal fraction of the cell and has been found in several mammalian tissues and in developing wheat endosperm.The embryo and aleurone layer of germinating seeds of the wheat cultivar Galahad showed PDI activity associated with a microsome-enriched fraction of cell homogenates PDI activity in microsome-enriched fractions from aleurone layers of normally germinating seeds was significantly higher than in their abnormally germinating counterparts and diminished as germination proceeded.Dry embryos and germinating embryos showed less PDI activity than aleurone layers. There was no significant difference in PDI activity between microsome-enriched fractions from embryos of normally and abnormally germinating seeds at 3 or 6 days of germination.Wheat aleurone PDI was partially purified using gel filtration and had a molecular mass of 110–130 kDa and a monomeric molecular mass of ca. 57 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis.

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Vacaru, Ana M., Fikadu G. Tafesse, Philipp Ternes, Vangelis Kondylis, Martin Hermansson, Jos F. H. M. Brouwers, Pentti Somerharju, Catherine Rabouille und Joost C. M. Holthuis. „Sphingomyelin synthase-related protein SMSr controls ceramide homeostasis in the ER“. Journal of Cell Biology 185, Nr. 6 (08.06.2009): 1013–27. http://dx.doi.org/10.1083/jcb.200903152.

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Ceramides are central intermediates of sphingolipid metabolism with critical functions in cell organization and survival. They are synthesized on the cytosolic surface of the endoplasmic reticulum (ER) and transported by ceramide transfer protein to the Golgi for conversion to sphingomyelin (SM) by SM synthase SMS1. In this study, we report the identification of an SMS1-related (SMSr) enzyme, which catalyses the synthesis of the SM analogue ceramide phosphoethanolamine (CPE) in the ER lumen. Strikingly, SMSr produces only trace amounts of CPE, i.e., 300-fold less than SMS1-derived SM. Nevertheless, blocking its catalytic activity causes a substantial rise in ER ceramide levels and a structural collapse of the early secretory pathway. We find that the latter phenotype is not caused by depletion of CPE but rather a consequence of ceramide accumulation in the ER. Our results establish SMSr as a key regulator of ceramide homeostasis that seems to operate as a sensor rather than a converter of ceramides in the ER.

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Vanlandschoot, Peter, Freya Van Houtte, Annelies Roobrouck, Ali Farhoudi, Felix Stelter, Darell L. Peterson, Julian Gomez-Gutierrez, Francisco Gavilanes und Geert Leroux-Roels. „LPS-binding protein and CD14-dependent attachment of hepatitis B surface antigen to monocytes is determined by the phospholipid moiety of the particles“. Journal of General Virology 83, Nr. 9 (01.09.2002): 2279–89. http://dx.doi.org/10.1099/0022-1317-83-9-2279.

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It was observed recently that recombinant yeast-derived hepatitis B surface antigen (rHBsAg) particles, which contain the S protein only, bind almost exclusively to monocytes. It is shown here that binding requires the presence of the LPS receptor CD14. Furthermore, evidence is presented that a domain on CD14 that is identical to or largely overlaps with the LPS-binding pocket is instrumental for the attachment of rHBsAg. Additionally, it is shown that the heat-labile LPS-binding protein (LBP) catalyses the binding of rHBsAg to the cells. Remarkably, natural plasma-derived HBsAg (pHBsAg) does not have this property. pHBsAg devoid of its lipids and reconstituted with phosphatidylserine or phosphatidylglycerol acquires the characteristic of yeast-derived HBsAg. Clearly, the interaction of rHBsAg with the cell membrane is determined by the presence of charged phospholipids that are absent in pHBsAg. Although a lipid–receptor interaction is suggested, antibody-inhibition experiments suggest a possible involvement of the C-terminal region of the S protein in the interaction with monocytes. The possible implications of these observations for hepatitis B virus (HBV) infection and HBV vaccine efficiency are discussed.

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Juge, Nathalie, Louise Tailford und C. David Owen. „Sialidases from gut bacteria: a mini-review“. Biochemical Society Transactions 44, Nr. 1 (09.02.2016): 166–75. http://dx.doi.org/10.1042/bst20150226.

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Sialidases are a large group of enzymes, the majority of which catalyses the cleavage of terminal sialic acids from complex carbohydrates on glycoproteins or glycolipids. In the gastrointestinal (GI) tract, sialic acid residues are mostly found in terminal location of mucins via α2-3/6 glycosidic linkages. Many enteric commensal and pathogenic bacteria can utilize sialic acids as a nutrient source, but not all express the sialidases that are required to release free sialic acid. Sialidases encoded by gut bacteria vary in terms of their substrate specificity and their enzymatic reaction. Most are hydrolytic sialidases, which release free sialic acid from sialylated substrates. However, there are also examples with transglycosylation activities. Recently, a third class of sialidases, intramolecular trans-sialidase (IT-sialidase), has been discovered in gut microbiota, releasing (2,7-anhydro-Neu5Ac) 2,7-anydro-N-acetylneuraminic acid instead of sialic acid. Reaction specificity varies, with hydrolytic sialidases demonstrating broad activity against α2,3-, α2,6- and α2,8-linked substrates, whereas IT-sialidases tend to be specific for α2,3-linked substrates. In this mini-review, we summarize the current knowledge on the structural and biochemical properties of sialidases involved in the interaction between gut bacteria and epithelial surfaces.

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Bura-Nakić, Elvira, Marija Marguš, Ivana Milanović, Darija Jurašin und Irena Ciglenečki. „The development of electrochemical methods for determining nanoparticles in the environment. Part II. Chronoamperometric study of FeS in sodium chloride solutions“. Environmental Chemistry 11, Nr. 2 (2014): 187. http://dx.doi.org/10.1071/en13090.

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Environmental contextIn anoxic environments FeS is both an important mediator in the Fe and S biogeochemical cycles and plays a vital role in controlling the scavenging and availability of many trace metals. Electrochemical detection of colloidal and particulate FeS in natural waters can be done by voltammetric measurements. The recorded anodic waves, however, are rather qualitative and lack information on the FeS concentration and size distribution. AbstractThe interactions of FeS nanoparticles (NPs) with a hanging mercury drop electrode in NaCl solutions were monitored by chronoamperometric measurements. Collisions of FeS NPs with the mercury surface were studied over a wide range of electrode potentials (between 0 and –1.9V v. Ag/AgCl). Faradaic impact transients were recorded only at the negative potentials (between –1.5 and –1.9V). It was shown that the mercury electrode surface modified with a FeS adlayer catalyses sodium reduction by shifting the potentials of this process to more positive values. This catalytic process together with possible hydrogen evolution is assumed to be the physicochemical basis for the determination of FeS NPs. Chronoamperometric measurements at the electrode potential of –1.9V showed that the reduction processes of sodium and hydrogen on FeS NPs upon collision are the main cause of sharp reduction current transients. At sufficiently positive electrode potentials (~–1.5V) the colliding FeS NPs would not be immediately repelled; instead they remained adhered to the mercury surface, causing ‘staircase-like’ chronoamperometric signals. It appears that recorded reduction current transients are carrying FeS NPs’ size information, which is consistent with parallel dynamic light scattering (DLS) measurements.

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Rajaram, O. V., R. Y. S. Chan und W. H. Sawyer. „Effect of unesterified cholesterol on the activity of cholesteryl ester transfer protein“. Biochemical Journal 304, Nr. 2 (01.12.1994): 423–30. http://dx.doi.org/10.1042/bj3040423.

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Cholesteryl ester transfer protein (CETP) catalyses the transfer of cholesteryl ester from high-density lipoprotein to triacylglycerol-rich lipoproteins and the transfer of triacylglycerols in the reverse direction. The activity of CETP has been studied using a continuous fluorescence assay which measures the excimer fluorescence of cholesteryl 1-pyrene decanoate in a synthetic donor microemulsion as the indicator of cholesteryl ester transfer. Emulsions were composed of cholesteryl oleate and egg phosphatidylcholine and had an average particle size of 14 +/- 1 nm as calculated from the molar volume of the components. The effect of changing the physical state of the emulsion surface was examined by including unesterified cholesterol in the donor and acceptor particles. The rate of CETP-induced transfer of the fluorescent cholesteryl ester between microemulsion particles increased when unesterified cholesterol was present at concentrations up to 17 mol% relative to phospholipid. The presence of cholesterol also changed the exchange kinetics from an apparent single-exponential to a double-exponential phenomenon. Binding of CETP to the emulsion surface was accompanied by an enhancement of fluorescence which was used to measure the binding equilibria. The enhancement of exchange due to the presence of cholesterol did not correlate with any increased binding of CETP to the emulsion surface. The presence of unesterified cholesterol in the donor did not affect the rate of transfer of the fluorescent cholesteryl ester when unlabelled emulsion was replaced by high-density lipoprotein as the acceptor. The studies demonstrate the use of microemulsions of defined size and composition for the study of the mechanism of action of CETP.

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Barnes, K., K. Shimada, M. Takahashi, K. Tanzawa und A. J. Turner. „Metallopeptidase inhibitors induce an up-regulation of endothelin-converting enzyme levels and its redistribution from the plasma membrane to an intracellular compartment“. Journal of Cell Science 109, Nr. 5 (01.05.1996): 919–28. http://dx.doi.org/10.1242/jcs.109.5.919.

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Endothelin-converting enzyme is a phosphoramidon-sensitive membrane metallopeptidase that catalyses the final step in biosynthesis of the potent vasoactive endothelin peptides. Immunomagnetic separation technology and immunohistochemistry have been used to demonstrate the co-localisation of endothelin-converting enzyme with the established ectoenzyme, aminopeptidase N, on the surface of endothelial cells. Unlike aminopeptidase N, however, endothelin-converting enzyme is seen to associate in clusters on the plasma membrane which can be distinguished from caveolae both biochemically and immunologically. Pre-treatment of endothelial cells with the metallopeptidase inhibitors phosphoramidon or thiorphan in the range 0.01-100 microM produced a dose-dependent increase in the levels of endothelin-converting enzyme protein and its accumulation in an intracellular compartment. No corresponding change in the levels of endothelin-converting enzyme-1 mRNA was detected under these conditions, nor in the levels of the closely related metalloenzyme, endopeptidase-24.11. The phosphoramidon and thiorphan-dependent increase is not due to direct inhibition of endothelin-converting enzyme not endopeptidase-24.11 but, rather, to an inhibition of the selective turnover of endothelin-converting enzyme protein.

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Naismith, James H. „Tryptophan oxygenation: mechanistic considerations“. Biochemical Society Transactions 40, Nr. 3 (22.05.2012): 509–14. http://dx.doi.org/10.1042/bst20120073.

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From a protein structural viewpoint, tryptophan is often considered an inert structural amino acid, playing a role as a hydrophobic anchor in membrane proteins or as part of the hydrophobic core of soluble proteins. However, tryptophan is the only polyaromatic amino acid and, from a chemical viewpoint, possesses unique reactivity owing to the electron-richness of the indole system. This reactivity is seen in the area of natural products and metabolites which have exquisite modifications of the indole ring system. Enzymes have evolved multiple strategies to break or modify the indole ring; one particular class is the IDO/TDO (indoleamine/tryptophan dioxygenase) superfamily. A new member of this family, PrnB, on the surface catalyses a very different reaction, but actually shares much of the early chemistry with the tryptophan dioxygenases. Studies on PrnB have contributed to our understanding of the wider superfamily. In the present mini-review, recent developments in our understanding of how the TDO class of enzymes use activated molecular oxygen to break the indole ring are discussed.

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