scholarly journals A Comparative Review on the Catalytic Mechanism of Nonheme Iron Hydroxylases and Halogenases

Catalysts ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 314 ◽  
Author(s):  
Amy Timmins ◽  
Sam P. de Visser
Keyword(s):  
Hydrogen Peroxide ◽  
Molecular Oxygen ◽  
Catalytic Mechanism ◽  
Computational Modelling ◽  
Active Species ◽  
Nonheme Iron ◽  
Comparative Review ◽  
Modelling Studies ◽  
Iron Heme ◽  
And Function

Enzymatic halogenation and haloperoxidation are unusual processes in biology; however, a range of halogenases and haloperoxidases exist that are able to transfer an aliphatic or aromatic C–H bond into C–Cl/C–Br. Haloperoxidases utilize hydrogen peroxide, and in a reaction with halides (Cl−/Br−), they react to form hypohalides (OCl−/OBr−) that subsequently react with substrate by halide transfer. There are three types of haloperoxidases, namely the iron-heme, nonheme vanadium, and flavin-dependent haloperoxidases that are reviewed here. In addition, there are the nonheme iron halogenases that show structural and functional similarity to the nonheme iron hydroxylases and form an iron(IV)-oxo active species from a reaction of molecular oxygen with α-ketoglutarate on an iron(II) center. They subsequently transfer a halide (Cl−/Br−) to an aliphatic C–H bond. We review the mechanism and function of nonheme iron halogenases and hydroxylases and show recent computational modelling studies of our group on the hectochlorin biosynthesis enzyme and prolyl-4-hydroxylase as examples of nonheme iron halogenases and hydroxylases. These studies have established the catalytic mechanism of these enzymes and show the importance of substrate and oxidant positioning on the stereo-, chemo- and regioselectivity of the reaction that takes place.

scholarly journals Assessment of the role of sutures in a lizard skull: a computer modelling study

2008 ◽  
Vol 276 (1654) ◽  
pp. 39-46 ◽  
Author(s):  
Mehran Moazen ◽  
Neil Curtis ◽  
Paul O'Higgins ◽  
Marc E.H Jones ◽  
Susan E Evans ◽  
...  
Keyword(s):  
Finite Element ◽  
Bone Growth ◽  
Computer Modelling ◽  
Computational Modelling ◽  
Complex Loading ◽  
Element Model ◽  
Element Analysis ◽  
Modelling Studies ◽  
And Function

Sutures form an integral part of the functioning skull, but their role has long been debated among vertebrate morphologists and palaeontologists. Furthermore, the relationship between typical skull sutures, and those involved in cranial kinesis, is poorly understood. In a series of computational modelling studies, complex loading conditions obtained through multibody dynamics analysis were imposed on a finite element model of the skull of Uromastyx hardwickii , an akinetic herbivorous lizard. A finite element analysis (FEA) of a skull with no sutures revealed higher patterns of strain in regions where cranial sutures are located in the skull. From these findings, FEAs were performed on skulls with sutures (individual and groups of sutures) to investigate their role and function more thoroughly. Our results showed that individual sutures relieved strain locally, but only at the expense of elevated strain in other regions of the skull. These findings provide an insight into the behaviour of sutures and show how they are adapted to work together to distribute strain around the skull. Premature fusion of one suture could therefore lead to increased abnormal loading on other regions of the skull causing irregular bone growth and deformities. This detailed investigation also revealed that the frontal–parietal suture of the Uromastyx skull played a substantial role in relieving strain compared with the other sutures. This raises questions about the original role of mesokinesis in squamate evolution.

scholarly journals RuIII(edta) complexes as molecular redox catalysts in chemical and electrochemical reduction of dioxygen and hydrogen peroxide: inner-sphere versus outer-sphere mechanism

RSC Advances ◽  
2021 ◽  
Vol 11 (35) ◽  
pp. 21359-21366
Author(s):  
Debabrata Chatterjee ◽  
Marta Chrzanowska ◽  
Anna Katafias ◽  
Maria Oszajca ◽  
Rudi van Eldik
Keyword(s):  
Hydrogen Peroxide ◽  
Electron Transfer ◽  
Electrochemical Reduction ◽  
Molecular Oxygen ◽  
Outer Sphere ◽  
Transfer Processes ◽  
Edta Complexes ◽  
Inner Sphere ◽  
Electron Transfer Processes ◽  
Sphere Mechanism

[RuII(edta)(L)]2–, where edta4– =ethylenediaminetetraacetate; L = pyrazine (pz) and H2O, can reduce molecular oxygen sequentially to hydrogen peroxide and further to water by involving both outer-sphere and inner-sphere electron transfer processes.

scholarly journals Cloning, Expression, and Purification of a Nitric Oxide Synthase-Like Protein fromBacillus cereus

2010 ◽  
Vol 2010 ◽  
pp. 1-4 ◽  
Author(s):  
Heather J. Montgomery ◽  
Andrea L. Dupont ◽  
Hilary E. Leivo ◽  
J. Guy Guillemette
Keyword(s):  
Nitric Oxide ◽  
Hydrogen Peroxide ◽  
Nitric Oxide Synthase ◽  
Expression And Purification ◽  
Spectral Shifts ◽  
Reconstituted System ◽  
Low Levels ◽  
And Function ◽  
Oxide Synthase ◽  
Reductase Domain

The nitric oxide synthase-like protein fromBacillus cereus(bcNOS) has been cloned, expressed, and characterized. This small hemeprotein (356 amino acids in length) has a mass of 43 kDa and forms a dimer. The recombinant protein showed similar spectral shifts to the mammalian NOS proteins and could bind the substrates L-arginine andNG-hydroxy-L-arginine as well as the ligand imidazole. Low levels of activity were recorded for the hydrogen peroxide-dependent oxidation ofNG-hydroxy-L-arginine and L-arginine by bcNOS, while a reconstituted system with the rat neuronal NOS reductase domain showed no activity. The recombinant bcNOS protein adds to the complement of bacterial NOS-like proteins that are used for the investigation of the mechanism and function of NO in microorganisms.

scholarly journals Adult and fetal haemoglobin J-Sardegna [α50(CE8)His→Asp]: functional and molecular modelling studies

2000 ◽  
Vol 346 (1) ◽  
pp. 193-199 ◽  
Author(s):  
Marcella CORDA ◽  
Maria C. DE ROSA ◽  
Maria G. PELLEGRINI ◽  
Maria T. SANNA ◽  
Alessandra OLIANAS ◽  
...  
Keyword(s):  
Functional Properties ◽  
Computational Modelling ◽  
Oxygen Affinity ◽  
Oxygen Binding ◽  
Structural Level ◽  
Fetal Haemoglobin ◽  
Significant Difference ◽  
Molecular Modelling Studies ◽  
Modelling Studies ◽  
2,3 Dpg

Haemoglobin (Hb) J-Sardegna [α50(CE8)His → Asp] is a haemoglobin variant characteristic of subjects from the island of Sardinia. Here we report a study of the functional properties of both fetal and adult Hb J-Sardegna. The results indicate that adult Hb J-Sardegna displays an oxygen affinity that is higher than that of adult Hb only in the presence of 2,3-diphosphoglycerate (2,3-DPG). On the contrary, at 20 °C, the oxygen affinity of fetal Hb J-Sardegna is identical to that of normal fetal haemoglobin, both in the presence and in the absence of 2,3-DPG. A significant difference between these two systems (i.e. a higher oxygen affinity of fetal Hb J-Sardegna) shows up very clearly only when temperature is increased to 37 °C. Hence in fetal Hb, the main effect of the amino acid substitution is a decrease in the overall enthalpy change of oxygenation. The results outline the role of the α1-β1 interface in assessing the thermodynamics of oxygen binding. The functional properties of both adult and fetal Hb J-Sardegna have been interpreted at the structural level in light of the results obtained by a computational modelling approach performed in comparison with HbA and Hb Aichi, a variant characterized by a different mutation [α50(CE8)His → Arg] at the same position.

Evolution of the active species and catalytic mechanism of Ti doped NaAlH 4 for hydrogen storage

2017 ◽  
Vol 42 (9) ◽  
pp. 6088-6095 ◽  
Author(s):  
Renjin Xiong ◽  
Ge Sang ◽  
Guanghui Zhang ◽  
Xiayan Yan ◽  
Peilong Li ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Catalytic Mechanism ◽  
Active Species

NADPH-dependent oxidation of CRMP2 through a MICAL1-Prx1 redox relay controls neurite outgrowth

2021 ◽  
Author(s):  
Clara Ortegón Salas ◽  
Yana Bodnar ◽  
Dennis Uhlenkamp ◽  
Katharina Schneider ◽  
Lara Knaup ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Neurite Outgrowth ◽  
Signaling Pathway ◽  
Molecular Oxygen ◽  
Effector Protein ◽  
Post Translational Modifications ◽  
Signal Transducers ◽  
Extracellular Signals ◽  
Cytoskeletal Dynamics ◽  
Redox Switch

Abstract CRMP2/DPYL2 is an effector protein in the semaphorin signaling pathway that controls cytoskeletal dynamics, linking extracellular signals to the formation of axonal networks. CRMP2 is regulated by post-translational modifications including a dithiol-disulfide redox switch. The mechanisms of reduction of this switch were established, the signal-induced oxidation, however, remained unclear. Here, we show that CRMP2 is oxidized through a redox relay involving the flavin-mooxygenase MICAL1 and the peroxidase Prx1 as specific signal transducers. Using molecular oxygen and electrons provided by NADPH, MICAL produces hydrogen peroxide and specifically oxidizes Prx1 through direct interactions between the proteins. Subsequently, Prx1 oxidizes CRMP2. The lack of any components of this redox relay dysregulates neurite outgrowth. Consequently, both oxidation and reduction of CRMP2 require reducing equivalents in the form of NADPH.

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