Editing Cytochrome c (section)

=== Superoxide detection ===

[[File:Peroxynitrous-acid-2D.svg|thumb|[[Peroxynitrous acid]]]]

Cytochrome c has been used to detect peroxide production in biological systems. As superoxide is produced, the number of oxidised cytochrome c<sup>3+</sup> increases, and reduced cytochrome c<sup>2+</sup> decreases.<ref>{{Cite journal |vauthors=McCord JM, Fridovich I |date=November 1969 |title=Superoxide dismutase. An enzymic function for erythrocuprein (hemocuprein) |journal=The Journal of Biological Chemistry |volume=244 |issue=22 |pages=6049–55 |doi=10.1016/S0021-9258(18)63504-5 |pmid=5389100 |doi-access=free}}</ref> However, superoxide is often produced with nitric oxide. In the presence of nitric oxide, the reduction of cytochrome c<sup>3+</sup> is inhibited.<ref name = "Thomson_1995">{{Cite journal |vauthors=Thomson L, Trujillo M, Telleri R, Radi R |date=June 1995 |title=Kinetics of cytochrome c<sup>2+</sup> oxidation by peroxynitrite: implications for superoxide measurements in nitric oxide-producing biological systems |journal=Archives of Biochemistry and Biophysics |volume=319 |issue=2 |pages=491–7 |doi=10.1006/abbi.1995.1321 |pmid=7786032}}</ref> This leads to the oxidisation of cytochrome c{{sup|2+}} to cytochrome c{{sup|3+}} by [[peroxynitrous acid]], an intermediate made through the reaction of nitric oxide and superoxide.<ref name="Thomson_1995" /> Presence of [[peroxynitrite]] or H{{sub|2}}O{{sub|2}} and [[nitrogen dioxide]] NO{{sub|2}} in the mitochondria can be lethal since they nitrate [[tyrosine]] residues of cytochrome c, which leads to disruption of cytochrome c's function as an electron carrier in the electron transport chain.<ref>{{Cite journal |vauthors=Domazou AS, Gebicka L, Didik J, Gebicki JL, van der Meijden B, Koppenol WH |date=April 2014 |title=The kinetics of the reaction of nitrogen dioxide with iron(II)- and iron(III) cytochrome c |journal=Free Radical Biology & Medicine |volume=69 |pages=172–80 |doi=10.1016/j.freeradbiomed.2014.01.014 |pmid=24447894}}</ref>