scholarly journals Benzylmalonyl-CoA dehydrogenase, an enzyme involved in bacterial auxin degradation

2021 ◽  
Author(s):  
Karola Schühle ◽  
Martin Saft ◽  
Bastian Vögeli ◽  
Tobias J. Erb ◽  
Johann Heider
Keyword(s):  
Electron Transfer ◽  
Reaction Mechanism ◽  
Electron Acceptor ◽  
Carboxy Group ◽  
Substrate Inhibition ◽  
Catalytic Efficiency ◽  
Electron Acceptors ◽  
Proton Abstraction ◽  
Simultaneous Oxidation ◽  
Acyl Coa Dehydrogenases

AbstractA novel acyl-CoA dehydrogenase involved in degradation of the auxin indoleacetate by Aromatoleum aromaticum was identified as a decarboxylating benzylmalonyl-CoA dehydrogenase (IaaF). It is encoded within the iaa operon coding for enzymes of indoleacetate catabolism. Using enzymatically produced benzylmalonyl-CoA, the reaction was characterized as simultaneous oxidation and decarboxylation of benzylmalonyl-CoA to cinnamoyl-CoA and CO2. Oxygen served as electron acceptor and was reduced to H2O2, whereas electron transfer flavoprotein or artificial dyes serving as electron acceptors for other acyl-CoA dehydrogenases were not used. The enzyme is homotetrameric, contains an FAD cofactor and is enantiospecific in benzylmalonyl-CoA turnover. It shows high catalytic efficiency and strong substrate inhibition with benzylmalonyl-CoA, but otherwise accepts only a few medium-chain alkylmalonyl-CoA compounds as alternative substrates with low activities. Its reactivity of oxidizing 2-carboxyacyl-CoA with simultaneous decarboxylation is unprecedented and indicates a modified reaction mechanism for acyl-CoA dehydrogenases, where elimination of the 2-carboxy group replaces proton abstraction from C2.

scholarly journals Benzylmalonyl-Coa Dehydrogenase, An Enzyme Involved in Bacterial Auxin Degradation

2021 ◽  
Author(s):  
Karola Schühle ◽  
Martin Saft ◽  
Bastian Vögeli ◽  
Tobias J. Erb ◽  
Johann Heider
Keyword(s):  
Electron Transfer ◽  
Reaction Mechanism ◽  
Electron Acceptor ◽  
Substrate Inhibition ◽  
Catalytic Efficiency ◽  
Electron Acceptors ◽  
Proton Abstraction ◽  
Simultaneous Oxidation ◽  
Auxin Catabolism ◽  
Acyl Coa Dehydrogenases

Abstract A novel acyl-CoA dehydrogenase involved in auxin degradation in Aromatoleum aromaticum was identified as a decarboxylating benzylmalonyl-CoA dehydrogenase (IaaF). It is encoded within the iaa operon coding for enzymes of auxin catabolism. Using enzymatically produced benzylmalonyl-CoA, the reaction was characterized as simultaneous oxidation and decarboxylation of benzylmalonyl-CoA to cinnamoyl-CoA and CO2. Oxygen served as electron acceptor and was reduced to H2O2, whereas electron transfer flavoprotein or artificial dyes serving as electron acceptors for other acyl-CoA dehydrogenases were not accepted. The enzyme is homotetrameric, contains an FAD cofactor and is enantiospecific in benzylmalonyl-CoA turnover. It shows high catalytic efficiency and strong substrate inhibition with benzylmalonyl-CoA, but otherwise accepts only a few medium-chain alkylmalonyl-CoA compounds as alternative substrates with low activities. Its reactivity of oxidizing 2-carboxyacyl-CoA with simultaneous decarboxylation is unprecedented and indicates a modified reaction mechanism for acyl-CoA dehydrogenases, where elimination of the 2-carboxy group replaces proton abstraction from C2.

scholarly journals Extracellular electron transfer-dependent anaerobic oxidation of ammonium by anammox bacteria

2019 ◽  
Author(s):  
Dario R. Shaw ◽  
Muhammad Ali ◽  
Krishna P. Katuri ◽  
Jeffrey A. Gralnick ◽  
Joachim Reimann ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Acceptor ◽  
Electron Acceptors ◽  
Extracellular Electron Transfer ◽  
Anammox Bacteria ◽  
Significant Finding ◽  
Ammonium Oxidation ◽  
Anaerobic Oxidation ◽  
Terminal Electron Acceptor ◽  
Carbon Based

AbstractAnaerobic ammonium oxidation (anammox) by anammox bacteria contributes significantly to the global nitrogen cycle, and plays a major role in sustainable wastewater treatment. Anammox bacteria convert ammonium (NH4+) to dinitrogen gas (N2) using nitrite (NO2−) or nitric oxide (NO) as the electron acceptor. In the absence of NO2− or NO, anammox bacteria can couple formate oxidation to the reduction of metal oxides such as Fe(III) or Mn(IV). Their genomes contain homologs of Geobacter and Shewanella cytochromes involved in extracellular electron transfer (EET). However, it is still unknown whether anammox bacteria have EET capability and can couple the oxidation of NH4+ with transfer of electrons to carbon-based insoluble extracellular electron acceptors. Here we show using complementary approaches that in the absence of NO2−, freshwater and marine anammox bacteria couple the oxidation of NH4+ with transfer of electrons to carbon-based insoluble extracellular electron acceptors such as graphene oxide (GO) or electrodes poised at a certain potential in microbial electrolysis cells (MECs). Metagenomics, fluorescence in-situ hybridization and electrochemical analyses coupled with MEC performance confirmed that anammox electrode biofilms were responsible for current generation through EET-dependent oxidation of NH4+. 15N-labelling experiments revealed the molecular mechanism of the EET-dependent anammox process. NH4+ was oxidized to N2 via hydroxylamine (NH2OH) as intermediate when electrode was the terminal electron acceptor. Comparative transcriptomics analysis supported isotope labelling experiments and revealed an alternative pathway for NH4+ oxidation coupled to EET when electrode is used as electron acceptor compared to NO2−as electron acceptor. To our knowledge, our results provide the first experimental evidence that marine and freshwater anammox bacteria can couple NH4+ oxidation with EET, which is a significant finding, and challenges our perception of a key player of anaerobic oxidation of NH4+ in natural environments and engineered systems.

On the role of gold nanoparticles in the selective photooxidation of 2-propanol over Au/TiO2

2015 ◽  
Vol 17 (16) ◽  
pp. 10391-10397 ◽  
Author(s):  
Alexander Lüken ◽  
Martin Muhler ◽  
Jennifer Strunk
Keyword(s):  
Gold Nanoparticles ◽  
Electron Transfer ◽  
Reaction Mechanism ◽  
Conduction Band ◽  
Electron Acceptor ◽  
Au Nanoparticles ◽  
Hole Capture ◽  
Insight Into

Partial insight into the reaction mechanism of the photooxidation of 2-propanol over Au/TiO2. 2-Propanol is activated by hole capture and converted to acetone requiring the presence of O2 as an electron acceptor. The deposited Au nanoparticles are assumed to facilitate the electron transfer from the TiO2 conduction band to adsorbed O2.

scholarly journals The reaction of mitochondrial l-3-glycerophosphate dehydrogenase with various electron acceptors

1969 ◽  
Vol 114 (1) ◽  
pp. 35-40 ◽  
Author(s):  
A P Dawson ◽  
C. J. R. Thorne
Keyword(s):  
Reaction Mechanism ◽  
Electron Acceptor ◽  
Maximum Velocity ◽  
Similar Type ◽  
Electron Acceptors ◽  
Phospholipase A ◽  
Glycerophosphate Dehydrogenase ◽  
Triton X ◽  
Kinetics Of ◽  
Enzyme Intermediate

1. The kinetics of the reaction of glycerophosphate dehydrogenase with a variety of electron acceptors have been investigated. 2. In all cases the reaction mechanism appears to involve a free modified-enzyme intermediate. 3. With some electron acceptors, the maximum velocity of the reaction and the Km for glycerophosphate are independent of the nature of the electron acceptor, whereas in other cases this is not so. 4. The reaction mechanism of the enzyme extracted with phospholipase A instead of with Triton X-100 is of a similar type.

scholarly journals Studies of Photoredox Reactions on Nanosize Semiconductors

1996 ◽  
Vol 452 ◽  
Author(s):  
Jess P. Wilcoxon ◽  
F. Parsapour ◽  
D. F. Kelley
Keyword(s):  
Electron Transfer ◽  
Band Gap ◽  
Electron Acceptor ◽  
Covalent Bonding ◽  
Electron Acceptors ◽  
Photoluminescence Spectroscopy ◽  
Time Resolved ◽  
Organic Electron ◽  
Time Resolved Photoluminescence ◽  
Kinetics Of

AbstractLight induced electron transfer (ET) from nanosize semiconductors of MoS2 to organic electron acceptors such as 2,2′-bipyridine (bpy) and methyl substituted 4,4′,5,5′-tetramethyl-2,2′-bipyridine (tmb) was studied by static and time resolved photoluminescence spectroscopy. The kinetics of ET were varied by changing the nanocluster size (the band gap), the electron acceptor, and the polarity of the solvent. MoS2is an especially interesting semiconductor material as it is an indirect semiconductor in bulk form, and has a layered covalent bonding arrangement which is highly resistant to photocorrosion.

Localization of Conduction Band Electrons in Polycrystalline Ti02 Studied by ESR

1981 ◽  
Vol 36 (3) ◽  
pp. 226-232 ◽  
Author(s):  
E. Serwicka ◽  
M. W. Schlierkamp ◽  
R. N. Schindler
Keyword(s):  
Activation Energy ◽  
Electron Transfer ◽  
Temperature Dependence ◽  
Conduction Band ◽  
Electron Acceptor ◽  
Electron Mobility ◽  
Signal Intensity ◽  
Esr Spectra ◽  
Electron Acceptors ◽  
Kcal Mole

Adsorption of electron acceptors on partially reduced TiO2 leads to the localization of mobile conduction band electrons which is indicated by the appearance of an ESR signal with g = 2.003. The localization process is accompanied by an electron transfer from donor centers in reduced TiO2 (Ti3+ ions) to adsorbed molecules. The ESR spectra show a decrease of the Ti3+ signal intensity at gr -1.96. Additionally, in the case of O2, SO2 and C6H5NO2 adsorption, the ESR signals of the respective anion radicals are observed. Illumination of samples with an electron acceptor adsorbed enhances the g - 2.003 signal. The activation energy corresponding to the temperature dependence of the localization process has been determined to be ~ 1 kcal/mole in the temperature range - 140 to - 40 °C. In the case of O2 and N2O the signal at g = 2.003 could be annihilated chemically by using propylene which reacted with the adsorbed electron acceptor and thus removed the species which reduced the electron mobility

Electron Donating and Acid-Base Properties of Cerium Oxide and Its Mixed Oxides with Alumina

1994 ◽  
Vol 59 (12) ◽  
pp. 2604-2610
Author(s):  
Sankaran Sugunan ◽  
Jacob M. Jalaja
Keyword(s):  
Electron Transfer ◽  
Cerium Oxide ◽  
Electron Acceptor ◽  
Electron Affinity ◽  
Mixed Oxides ◽  
Surface Acidity ◽  
Electron Acceptors ◽  
Oxide Surface ◽  
Acid Base ◽  
Titration Method

The electron donating properties of ceria activated at 300, 500 and 800 °C and its mixed oxides with alumina are reported from the studies on adsorption of electron acceptors of various electron affinity. The surface acidity/basicity of the oxides have been determined by titration method and H0,max values are reported. The limit of electron transfer from oxide surface is between 1.77 and 2.40 eV in terms of the electron affinity of the electron acceptor. Ceria promotes the electron donating of alumina without changing the limit of electron transfer.

The influence of potassium dichromate on dissimilatory reduction of sulfate and nitrate ions by bacteria Desulfovibrio sp.

2017 ◽  
Vol 28 (1-2) ◽  
pp. 84-95
Author(s):  
O. M. Moroz ◽  
S. O. Hnatush ◽  
Ch. I. Bohoslavets ◽  
T. M. Hrytsun’ ◽  
B. M. Borsukevych
Keyword(s):  
Electron Acceptor ◽  
Potassium Dichromate ◽  
Anaerobic Respiration ◽  
Sulfate Reducing Bacteria ◽  
Negative Influence ◽  
Electron Acceptors ◽  
Metal Compounds ◽  
Nitrate Ions ◽  
Sulfate Reducing ◽  
Reducing Bacteria

Sulfate reducing bacteria, capable to reductive transformation of different nature pollutants, used in biotechnologies of purification of sewage, contaminated by carbon, sulfur, nitrogen and metal compounds. H2S formed by them sediment metals to form of insoluble sulfides. Number of metals can be used by these microorganisms as electron acceptors during anaerobic respiration. Because under the influence of metal compounds observed slowing of bacteria metabolism, selection isolated from technologically modified ecotops resistant to pollutions strains is important task to create a new biotechnologies of purification. That’s why the purpose of this work was to study the influence of potassium dichromate, present in medium, on reduction of sulfate and nitrate ions by sulfate reducing bacteria Desulfovibrio desulfuricans IMV K-6, Desulfovibrio sp. Yav-6 and Desulfovibrio sp. Yav-8, isolated from Yavorivske Lake, to estimate the efficiency of possible usage of these bacteria in technologies of complex purification of environment from dangerous pollutants. Bacteria were cultivated in modified Kravtsov-Sorokin medium without SO42- and FeCl2×4H2O for 10 days. To study the influence of K2Cr2O7 on usage by bacteria SO42- or NO3- cells were seeded to media with Na2SO4×10H2O or NaNO3 and K2Cr2O7 at concentrations of 1.74 mM for total content of electron acceptors in medium 3.47 mM (concentration of SO42- in medium of standard composition). Cells were also seeded to media with 3.47 mM Na2SO4×10H2O, NaNO3 or K2Cr2O7 to investigate their growth in media with SO42-, NO3- or Cr2O72- as sole electron acceptor (control). Biomass was determined by turbidymetric method, content of sulfate, nitrate, dichromate, chromium (III) ions, hydrogen sulfide or ammonia ions in cultural liquid – by spectrophotometric method. It was found that K2Cr2O7 inhibits growth (2.2 and 1.3 times) and level of reduction by bacteria sulfate or nitrate ions (4.2 and 3.0 times, respectively) at simultaneous addition into cultivation medium of 1.74 mM SO42- or NO3- and 1.74 mM Cr2O72-, compared with growth and level of reduction of sulfate or nitrate ions in medium only with SO42- or NO3- as sole electron acceptor. Revealed that during cultivation of bacteria in presence of equimolar amount of SO42- or NO3- and Cr2O72-, last used by bacteria faster, content of Cr3+ during whole period of bacteria cultivation exceeded content H2S or NH4+. K2Cr2O7 in medium has most negative influence on dissimilatory reduction by bacteria SO42- than NO3-, since level of nitrate ions reduction by cells in medium with NO3- and Cr2O72- was a half times higher than level of sulfate ions reduction by it in medium with SO42- and Cr2O72-. The ability of bacteria Desulfovibrio sp. to priority reduction of Cr2O72- and after their exhaustion − NO3- and SO42- in the processes of anaerobic respiration can be used in technologies of complex purification of environment from toxic compounds.

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