Nitric oxide and cytochrome oxidase: reaction mechanisms from the enzyme to the cell.
The aim of this work is to review the information available on the molecular mechanisms by which the NO radical reversibly downregulates the function of cytochrome c oxidase (CcOX). The mechanisms of the reactions with NO elucidated over the past few years are described and discussed in the context of the inhibitory effects on the enzyme activity. Two alternative reaction pathways are presented whereby NO reacts with the catalytic intermediates of CcOX populated during turnover. The central idea is that at "cellular" concentrations of NO (</= microM), the redox state of the respiratory chain results in the formation of either the nitrosyl- or the nitrite-derivative of CcOX, with potentially different metabolic implications for the cell. In particular, the role played by CcOX in protecting the cell from excess NO, potentially toxic for mitochondria, is also reviewed highlighting the mechanistic differences between eukaryotes and some prokaryotes.
Sarti
Paolo
P
Department of Biochemical Sciences and CNR Institute of Molecular Biology and Pathology, University of Rome La Sapienza, Rome, Italy. paolo.sarti@uniroma1.it
Giuffrè
Alessandro
A
Barone
Maria Cecilia
MC
Forte
Elena
E
Mastronicola
Daniela
D
Brunori
Maurizio
M
D000818:Animals; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005057:Eukaryotic Cells / Q000201:enzymology*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D011387:Prokaryotic Cells / Q000201:enzymology*
D009569:Nitric Oxide; D003576:Electron Transport Complex IV