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Mechanisms for enzy...
Mechanisms for enzymatic reduction of nitric oxide to nitrous oxide - A comparison between nitric oxide reductase and cytochrome c oxidase
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- Blomberg, Margareta R. A. (författare)
- Stockholms universitet,Institutionen för organisk kemi
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- Ädelroth, Pia (författare)
- Stockholms universitet,Institutionen för biokemi och biofysik
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(creator_code:org_t)
- Elsevier BV, 2018
- 2018
- Engelska.
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - : Elsevier BV. - 0005-2728 .- 1879-2650. ; 1859:11, s. 1223-1234
- Relaterad länk:
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https://doi.org/10.1...
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- Cytochrome c oxidases (CcO) reduce O-2 to H2O in the respiratory chain of mitochondria and many aerobic bacteria. In addition, some species of CcO can also reduce NO to N2O and water while others cannot. Here, the mechanism for NO-reduction in CcO is investigated using quantum mechanical calculations. Comparison is made to the corresponding reaction in a true cytochrome c-dependent NO reductase (cNOR). The calculations show that in cNOR, where the reduction potentials are low, the toxic NO molecules are rapidly reduced, while the higher reduction potentials in CcO lead to a slower or even impossible reaction, consistent with experimental observations. In both enzymes the reaction is initiated by addition of two NO molecules to the reduced active site, forming a hyponitrite intermediate. In cNOR, N2O can then be formed using only the active-site electrons. In contrast, in CcO, one proton-coupled reduction step most likely has to occur before N2O can be formed, and furthermore, proton transfer is most likely rate-limiting. This can explain why different CcO species with the same heme alpha(3)-Cu active site differ with respect to NO reduction efficiency, since they have a varying number and/or properties of proton channels. Finally, the calculations also indicate that a conserved active site valine plays a role in reducing the rate of NO reduction in CcO.
Ämnesord
- NATURVETENSKAP -- Biologi (hsv//swe)
- NATURAL SCIENCES -- Biological Sciences (hsv//eng)
- NATURVETENSKAP -- Kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences (hsv//eng)
Nyckelord
- Heme-copper oxidases
- NO reduction
- Density functional theory
- Reduction potentials
- Reaction mechanisms
- Energy profiles
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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