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Nitric Oxide Reductase (nitric + oxide_reductase)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Design of a Functional Nitric Oxide Reductase within a Myoglobin Scaffold

CHEMBIOCHEM, Issue 8 2010
Valentin Köhler Dr.
One site fits all: Yi Lu and co-workers have reported the conversion of sperm-whale myoglobin into a functional nitric oxide reductase. For this purpose, they designed a second metal binding site in the wild-type holo-protein and demonstrated NO reduction with the structurally characterized model, making thereby a significant contribution to the rapidly developing field of artificial metalloenzymes. [source]

Electronic structure of iron(II),porphyrin nitroxyl complexes: Molecular mechanism of fungal nitric oxide reductase (P450nor)

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 12 2006
Nicolai Lehnert
Abstract Density functional calculations are employed to investigate key intermediates of the catalytic cycle of fungal nitric oxide reductase (P450nor). The formal Fe(II),nitroxyl species Fe(II)NO/(,) can principally exist in the two spin-states S = 0 and S = 1. In the S = 0 case, a very covalent FeNO , bond is present, which leads to an electronic structure description that is actually intermediate between Fe(I)NO and Fe(II)NO,. In contrast, the S = 1 case shows a ferrous Fe(II)NO complex with the extra electron being stored in the , system of the porphyrin ligand. Importantly, the Fe(II)NO/(,) species are very basic. The electronic structures and spectroscopic properties of the corresponding N- and O-protonated forms are very different, and unequivocally show that the Mb,HNO adduct (Mb-Myoglobin) prepared by farmer and coworkers is in fact N-protonated. The presence of an axial thiolate ligand enables a second protonation leading to the corresponding Fe(IV)NHOH, species, which is identified with the catalytically active intermediate I of P450nor. This species reacts with a second molecule of NO by initial electron transfer from NO to Fe(IV) followed by addition of NO+ forming an NN bond. This is accompanied by an energetically very favorable intramolecular proton transfer leading to the generation of a quite stable Fe(III)N(OH)(NOH) complex. This way, the enzyme is able to produce dimerized HNO under very controlled conditions and to prevent loss of this ligand from Fe(III). The energetically disfavoured tautomer Fe(III)N(OH2)(NO) is the catalytically productive species that spontaneously cleaves the NOH2 bond forming N2O and H2O in a highly exergonic reaction. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1338,1351, 2006 [source]

Design of a Functional Nitric Oxide Reductase within a Myoglobin Scaffold

Isotopologue fractionation during N2O production by fungal denitrification

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2008
Robin L. Sutka
Identifying the importance of fungi to nitrous oxide (N2O) production requires a non-intrusive method for differentiating between fungal and bacterial N2O production such as natural abundance stable isotopes. We compare the isotopologue composition of N2O produced during nitrite reduction by the fungal denitrifiers Fusarium oxysporum and Cylindrocarpon tonkinense with published data for N2O production during bacterial nitrification and denitrification. The fractionation factors for bulk nitrogen isotope values for fungal denitrification were in the range ,74.7 to ,6.6,. There was an inverse relationship between the absolute value of the fractionation factors and the reaction rate constant. We interpret this in terms of variation in the relative importance of the rate constants for diffusion and enzymatic reduction in controlling the net isotope effect for N2O production during fungal denitrification. Over the course of nitrite reduction, the ,18O values for N2O remained constant and did not exhibit a relationship with the concentration characteristic of an isotope effect. This probably reflects isotopic exchange with water. Similar to the ,18O data, the site preference (SP; the difference in ,15N between the central and outer N atoms in N2O) was unrelated to concentration during nitrite reduction and, therefore, has the potential to act as a conservative tracer of production from fungal denitrification. The SP values of N2O produced by F. oxysporum and C. tonkinense were 37.1,±,2.5, and 36.9,±,2.8,, respectively. These SP values are similar to those obtained in pure culture studies of bacterial nitrification but quite distinct from SP values for bacterial denitrification. The large magnitude of the bulk nitrogen isotope fractionation and the ,18O values associated with fungal denitrification are distinct from bacterial production pathways; thus multiple isotopologue data holds much promise for resolving bacterial and fungal production. Our work further provides insight into the role that fungal and bacterial nitric oxide reductases have in determining site preference during N2O production. Copyright © 2008 John Wiley & Sons, Ltd. [source]