Editing Oxidative phosphorylation (section)

=== Cytochrome c oxidase (complex IV) ===
{{further|cytochrome c oxidase}}
[[File:Complex IV.svg|thumb|right|Complex IV: [[cytochrome c oxidase]].]]

[[Cytochrome c oxidase]], also known as ''complex IV'', is the final protein complex in the electron transport chain.<ref>{{cite journal | vauthors = Calhoun MW, Thomas JW, Gennis RB | title = The cytochrome oxidase superfamily of redox-driven proton pumps | journal = Trends in Biochemical Sciences | volume = 19 | issue = 8 | pages = 325–330 | date = August 1994 | pmid = 7940677 | doi = 10.1016/0968-0004(94)90071-X }}</ref> The mammalian enzyme has an extremely complicated structure and contains 13 subunits, two heme groups, as well as multiple metal ion cofactors&nbsp;– in all, three atoms of [[copper]], one of [[magnesium]] and one of [[zinc]].<ref>{{cite journal | vauthors = Tsukihara T, Aoyama H, Yamashita E, Tomizaki T, Yamaguchi H, Shinzawa-Itoh K, Nakashima R, Yaono R, Yoshikawa S | title = The whole structure of the 13-subunit oxidized cytochrome c oxidase at 2.8 A | journal = Science | volume = 272 | issue = 5265 | pages = 1136–1144 | date = May 1996 | pmid = 8638158 | doi = 10.1126/science.272.5265.1136 | s2cid = 20860573 | bibcode = 1996Sci...272.1136T }}</ref>

This enzyme mediates the final reaction in the electron transport chain and transfers electrons to oxygen and hydrogen (protons), while pumping protons across the membrane.<ref>{{cite journal | vauthors = Yoshikawa S, Muramoto K, Shinzawa-Itoh K, Aoyama H, Tsukihara T, Shimokata K, Katayama Y, Shimada H | title = Proton pumping mechanism of bovine heart cytochrome c oxidase | journal = Biochimica et Biophysica Acta (BBA) - Bioenergetics | volume = 1757 | issue = 9–10 | pages = 1110–1116 | year = 2006 | pmid = 16904626 | doi = 10.1016/j.bbabio.2006.06.004 | doi-access = free }}</ref> The final [[electron acceptor]] oxygen is reduced to water in this step. Both the direct pumping of protons and the consumption of matrix protons in the reduction of oxygen contribute to the proton gradient. The reaction catalyzed is the oxidation of cytochrome c and the reduction of oxygen:

{{NumBlk|:|<chem>4 Cyt\,c_{red}{} + O2{} + 8H+_{matrix} -> 4 Cyt\,c_{ox}{} + 2H2O{} + 4H+_{intermembrane}</chem>|{{EquationRef|5}}}}