scholarly journals Photoreduction of membrane-bound paramagnetic component X by water as electron donor

FEBS Letters ◽  
1979 ◽  
Vol 98 (2) ◽  
pp. 381-385 ◽  
Author(s):  
Tetsuo Hiyama ◽  
Harry Y. Tsujimoto ◽  
Daniel I. Arnon
Keyword(s):  
Electron Donor ◽  
Paramagnetic Component ◽  
Membrane Bound

Characterization of the Metamitron Deaminating Enzyme Activity from Sugar Beet ( Beta vulgaris L.) Leaves

1979 ◽  
Vol 34 (11) ◽  
pp. 948-950 ◽  
Author(s):  
Carl Fedtke ◽  
Robert R. Schmidt
Keyword(s):  
Cytochrome C ◽  
Sugar Beet ◽  
Electron Donor ◽  
Nitrogen Atmosphere ◽  
Enzyme Preparations ◽  
Reducing Conditions ◽  
Trade Name ◽  
Membrane Bound

Abstract The enzymatic activity from sugar beet leaves which is responsible for the detoxification of the herbicide metamitron (4-amino-4,5-dihydro-3-methyl-6-phenyl-1, 2, 4-triazin-5-one, trade name Goltix®) has been characterized in vitro. The detoxification occurs by rapid deamination in vivo as well as in vitro. However, the deamination in vitro is only maximal under reducing conditions, i. e. with an electron donor and in a nitrogen atmosphere. The electron donor may be cystein, glutathione, dithionite or ascorbate. The enzymatic deamination further requires the addition of cytochrome c and a “supernatant factor”, which may be replaced by FMN, FAD or DCPIP. However, in the presence of FMN or DCPIP cytochrome c is not essential but only stimulatory. The partic­ulate as well as the soluble metamitron deaminating enzyme preparations obtained take up oxygen when supplied with cysteine and FMN. The particulate enzyme appears in the peroxysome-fraction. It is therefore suggested, that the enzymatic deamination of metamitron in sugar beet leaves is mediated by a proxisomal membrane bound electron transport system which alternatively may reduce oxygen or metamitron (deaminating).

scholarly journals Oxygen reduction in the strict anaerobe Desulfovibrio vulgaris Hildenborough: characterization of two membrane-bound oxygen reductases

Microbiology ◽  
2011 ◽  
Vol 157 (9) ◽  
pp. 2720-2732 ◽  
Author(s):  
O. Lamrabet ◽  
L. Pieulle ◽  
C. Aubert ◽  
F. Mouhamar ◽  
P. Stocker ◽  
...  
Keyword(s):  
Electron Donor ◽  
Desulfovibrio Vulgaris ◽  
Strictly Anaerobic ◽  
Quinol Oxidase ◽  
Genes Encoding ◽  
Oxygen Reductase ◽  
Membrane Bound ◽  
Carbon Monoxide Binding ◽  
Cellular Compartments ◽  
Encoding Genes

Although Desulfovibrio vulgaris Hildenborough (DvH) is a strictly anaerobic bacterium, it is able to consume oxygen in different cellular compartments, including extensive periplasmic O2 reduction with hydrogen as electron donor. The genome of DvH revealed the presence of cydAB and cox genes, encoding a quinol oxidase bd and a cytochrome c oxidase, respectively. In the membranes of DvH, we detected both quinol oxygen reductase [inhibited by heptyl-hydroxyquinoline-N-oxide (HQNO)] and cytochrome c oxidase activities. Spectral and HPLC data for the membrane fraction revealed the presence of o-, b- and d-type haems, in addition to a majority of c-type haems, but no a-type haem, in agreement with carbon monoxide-binding analysis. The cytochrome c oxidase is thus of the cc(o/b)o 3 type, a type not previously described. The monohaem cytochrome c 553 is an electron donor to the cytochrome c oxidase; its encoding gene is located upstream of the cox operon and is 50-fold more transcribed than coxI encoding the cytochrome c oxidase subunit I. Even when DvH is grown under anaerobic conditions in lactate/sulfate medium, the two terminal oxidase-encoding genes are expressed. Furthermore, the quinol oxidase bd-encoding genes are more highly expressed than the cox genes. The cox operon exhibits an atypical genomic organization, with the gene coxII located downstream of coxIV. The occurrence of these membrane-bound oxygen reductases in other strictly anaerobic Deltaproteobacteria is discussed.

Comparison between the nitric oxide reductase family and its aerobic relatives, the cytochrome oxidases

2002 ◽  
Vol 30 (4) ◽  
pp. 662-667 ◽  
Author(s):  
S. de Vries ◽  
I. Schröder
Keyword(s):  
Electron Donor ◽  
Gram Negative Bacteria ◽  
Nitric Oxide Reductase ◽  
Entry Site ◽  
Gram Negative ◽  
Hyperthermophilic Archaeon ◽  
Modular Evolution ◽  
Cytochrome Oxidases ◽  
Membrane Bound ◽  
Dependent Type

The denitrification pathway has been studied in the hyperthermophilic archaeon Pyrobaculum aerophilum. In contrast with Gram-negative bacteria, all four denitrification enzymes are membrane-bound. P. aerophilum is also the only denitrifyer identified so far in which menaquinol is the electron donor to all four denitrification reductases. The NO reductase (NOR) of P. aerophilum belongs to the superfamily of haem-copper oxidases and is of the qNOR (quinol-dependent) type. Three types of NOR have been purified so far: cNOR (cytochrome c/pseudoazurin-dependent), qNOR and qCuANOR (qNOR that contains CuA at the electron entry site). It is proposed that the NORs and the various cytochrome oxidases have evolved by modular evolution, in view of the structure of their electron donor sites. qNOR is further proposed to be the ancestor of all NORs and cytochrome oxidases belonging to the superfamily of haem-copper oxidases.

scholarly journals Purification and Characterization of a Membrane-Bound Hydrogenase from the Hyperthermophilic ArchaeonPyrococcus furiosus

2000 ◽  
Vol 182 (12) ◽  
pp. 3423-3428 ◽  
Author(s):  
Rajat Sapra ◽  
Marc F. J. M. Verhagen ◽  
Michael W. W. Adams
Keyword(s):  
Electron Donor ◽  
Rhodospirillum Rubrum ◽  
Sequence Similarity ◽  
Methanosarcina Barkeri ◽  
Hydrogenase Activity ◽  
Sequence Information ◽  
Genome Database ◽  
Α Subunit ◽  
Membrane Bound ◽  
Α And Β Subunits

ABSTRACT Highly washed membrane preparations from cells of the hyperthermophilic archaeon Pyrococcus furiosus contain high hydrogenase activity (9.4 μmol of H2 evolved/mg at 80°C) using reduced methyl viologen as the electron donor. The enzyme was solubilized with n-dodecyl-β-d-maltoside and purified by multistep chromatography in the presence of Triton X-100. The purified preparation contained two major proteins (α and β) in an approximate 1:1 ratio with a minimum molecular mass near 65 kDa and contained ∼1 Ni and 4 Fe atoms/mol. The reduced enzyme gave rise to an electron paramagnetic resonance signal typical of the so-called Ni-C center of mesophilic NiFe-hydrogenases. Neither highly washed membranes nor the purified enzyme used NAD(P)(H) or P. furiosus ferredoxin as an electron carrier, nor did either catalyze the reduction of elemental sulfur with H2 as the electron donor. Using N-terminal amino acid sequence information, the genes proposed to encode the α and β subunits were located in the genome database within a putative 14-gene operon (termedmbh). The deduced sequences of the two subunits (Mbh 11 and 12) were distinctly different from those of the four subunits that comprise each of the two cytoplasmic NiFe-hydrogenases of P. furiosus and show that the α subunit contains the NiFe-catalytic site. Six of the open reading frames (ORFs) in the operon, including those encoding the α and β subunits, show high sequence similarity (>30% identity) with proteins associated with the membrane-bound NiFe-hydrogenase complexes from Methanosarcina barkeri, Escherichia coli, and Rhodospirillum rubrum. The remaining eight ORFs encode small (<19-kDa) hypothetical proteins. These data suggest that P. furiosus, which was thought to be solely a fermentative organism, may contain a previously unrecognized respiratory system in which H2metabolism is coupled to energy conservation.

Cytochrome composition and oxygen-dependent respiration-driven proton translocation in Wolinella curva, Wolinella recta, Bacteroides ureolyticus, and Bacteroides gracilis

1992 ◽  
Vol 38 (2) ◽  
pp. 104-110 ◽  
Author(s):  
Yeong-Hwan Han ◽  
Robert M. Smibert ◽  
Noel R. Krieg
Keyword(s):  
Cytochrome C ◽  
Key Words ◽  
Cytochrome B ◽  
Electron Donor ◽  
Proton Translocation ◽  
Proton Efflux ◽  
Membrane Bound ◽  
Type Strains

The membrane fractions of the microaerobically grown type strains of Wolinella curva, Wolinella recta, Bacteroides ureolyticus, and Bacteroides gracilis contained membrane-bound cytochrome b, cytochrome c, and CO-binding cytochrome c. Soluble cytochrome c and CO-binding cytochrome c were also present. Although B. gracilis is oxidase negative, it possessed cytochrome c. With H2 or formate as the electron donor, proton efflux from anaerobic cells occurred upon addition of a pulse of oxygen. With formate as the electron donor, the H+/O ratios of W. curva, W. recta, B. ureolyticus, and B. gracilis were 0.75, 1.66, 2.06, and 2.04, respectively. With H2 as the electron donor, the H+/O ratios of W. curva, B. ureolyticus, and B. gracilis were 1.25, 1.97, and 2.36, respectively. Proton translocation was inhibited by the protonophore carbonylcyanide m-chlorophenylhydrazone. The results confirm that the organisms are not anaerobes but are microaerophiles capable of respiring with oxygen. Key words: cytochrome, proton, Wolinella, Bacteroides, microaerophile.

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