Sitokrom c oksidase: Perbedaan antara revisi
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Baris 1:
[[Berkas:Cytochrome_C_Oxidase_1OCC_in_Membrane_2.png|jmpl|ka|200px|Struktur kristal sitokrom c oksidase]]
'''Oksidase CC''' ({{lang-en|cytochrome c oxidase, COX}}) adalah kompleks [[enzim]] dengan berkas [[gen|genetik]] berjumlah 3 pada [[mitokondria]] dengan fungsi transfer elektron,<ref>{{en}}{{cite web▼
▲'''Oksidase CC''' ({{lang-en|EC.1.9.3.1, cytochrome c oxidase, CcO, COX}}) adalah kompleks [[enzim]] dengan berkas [[gen
| url = http://www.ncbi.nlm.nih.gov/pubmed/9694260
| title = Transcriptional regulation of mammalian cytochrome c oxidase genes
| accessdate = 2010-11-14
| work = Center for Molecular Medicine and Genetics, Wayne State University School of Medicine; Grossman LI, Seelan RS, Jaradat SA.
}}</ref> dan 10 buah pada [[DNA]] dalam [[inti sel]] [[eukariota]].<ref>{{en}} {{cite web
| url = http://www.ncbi.nlm.nih.gov/pubmed/16760263
| title = Assembly of mitochondrial cytochrome c-oxidase, a complicated and highly regulated cellular process
| accessdate = 2010-11-14
| work = Departments of Neurology, The John T. Macdonald Foundation Center for Medical Genetics, University of Miami Miller School of Medicine; Fontanesi F, Soto IC, Horn D, Barrientos A.
}}</ref> [[ekspresi gen]]etik pada [[hepatosit]] [[hewan]] [[sapi]] adalah:
* 5 [[fosfatidil etanolamina]]
* 3 [[fosfatidil gliserol]]
* 2 [[asam kolat]]
* 2 [[heme]] A
* 3 [[tembaga|Cu]]
* 1 [[magnesium|Mg]]
* 1 [[seng|Zn]]
dengan 2 [[kanal proton]] yang terbentang dari matriks [[mitokondria]] menuju [[sitoplasma]].<ref>{{en}} {{cite web
| url = http://www.ncbi.nlm.nih.gov/pubmed/8638158
| title = The whole structure of the 13-subunit oxidized cytochrome c oxidase at 2.8 A
| accessdate = 2010-11-15
| work = Institute for Protein Research, Osaka University; Tsukihara T, Aoyama H, Yamashita E, Tomizaki T, Yamaguchi H, Shinzawa-Itoh K, Nakashima R, Yaono R, Yoshikawa S.
}}</ref>
[[Reaksi redoks]] yang berlangsung:
:<math> 4\mbox{cyt.c}^{2+} \rightarrow 4\mbox{cyt.c}^{3+} + 4\mbox{e}^- \, </math>
Baris 22 ⟶ 38:
Keterangan:
* cyt.c adalah [[sitokrom c]]
Pada lintasan D, setelah molekul O<sub>2</sub> terikat pada situs reduksi yang berupa kompleks Fe<sup>2+</sup>(a3) dan Cu(B), O<sub>2</sub> segera tereduksi menjadi O<sub>2</sub><sup>-</sup> dan membentuk [[ikatan hidrogen]] dengan CN<sup>-</sup> dan [[gugus fungsional|gugus]] [[hidroksil|OH<sup>-</sup>]] [[tirosina|Tyr244]] hingga memungkinkan O<sub>2</sub><sup>-</sup> menerima 3 tambahan elektron dari Cu1B<sup>+</sup>, Fe<sup>3+</sup>(a3), dan Tyr-OH,<ref>{{en}} {{cite web
| url = http://www.ncbi.nlm.nih.gov/pubmed/20385840
| title = Bovine cytochrome c oxidase structures enable O2 reduction with minimization of reactive oxygens and provide a proton-pumping gate
| accessdate = 2010-11-15
| work = Department of Life Science, University of Hyogo; Muramoto K, Ohta K, Shinzawa-Itoh K, Kanda K, Taniguchi M, Nabekura H, Yamashita E, Tsukihara T, Yoshikawa S.
}}</ref> di bawah regulasi [[histidina]].<ref name="PM16829226">{{en}} {{cite web
| url = http://www.ncbi.nlm.nih.gov/pubmed/16829226
| title = Reaction mechanism of bovine heart cytochrome c oxidase
| accessdate = 2010-11-15
| work = Department of Life Science, University of Hyogo; Yoshikawa S, Muramoto K, Shinzawa-Itoh K, Aoyama H, Tsukihara T, Ogura T, Shimokata K, Katayama Y, Shimada H.
}}</ref> Keempat elektron tersebut berasal dari [[sitokrom c|Fe<sup>2+</sup>(c)]].<ref name="PM12765763">{{en}} {{cite web
| url = http://www.ncbi.nlm.nih.gov/pubmed/12765763
| title = Water-gated mechanism of proton translocation by cytochrome c oxidase
| accessdate = 2010-11-15
| work = Helsinki Bioenergetics Group, Institute of Biotechnology and Biocentrum Helsinki, University of Helsinki; Wikström M, Verkhovsky MI, Hummer G.
}}</ref> Pasokan [[ion]] [[hidrogen|H<sup>+</sup>]] dibawa oleh kluster 5 [[molekul]] air,<ref>{{en}} {{cite web
| url = http://www.ncbi.nlm.nih.gov/pubmed/17309257
| title = Storage of an excess proton in the hydrogen-bonded network of the d-pathway of cytochrome C oxidase: identification of a protonated water cluster
| accessdate = 2010-11-15
| work = Department of Chemistry and Center for Biophysical Modeling and Simulation; Xu J, Sharpe MA, Qin L, Ferguson-Miller S, Voth GA.
}}</ref> dari [[asam glutamat|Glu286]] di dalam matriks, untuk mereduksi [[oksigen|O<sub>2</sub>]] tersebut menjadi [[air|H<sub>2</sub>O]]. Setelah oksigen selesai tereduksi, kelebihan ion H<sup>+</sup> akan dihantarkan ke gugus [[delta-propionat]] dari Fe<sup>2+</sup>(a3).
Sifat [[hidrofobik]] gugus [[delta-propionat]] dan ikatan hidrogen yang dibentuknya dengan senyawa [[asam aspartat|Asp51]] yang terletak pada ruang antarmembran memungkinkan letupan ion H<sup>+</sup> dari gugus tersebut sebagai reaksi oksidasi, dengan reaksi reduksi Asp51 menjadi [[asparagina]].<ref name="PM16829226" /><ref>{{en}} {{cite web
| url = http://www.ncbi.nlm.nih.gov/pubmed/16904626
| title = Proton pumping mechanism of bovine heart cytochrome c oxidase
| accessdate = 2010-11-15
| work = Department of Life Science, University of Hyogo; Yoshikawa S, Muramoto K, Shinzawa-Itoh K, Aoyama H, Tsukihara T, Shimokata K, Katayama Y, Shimada H.
}}</ref> 4 [[ion]] [[hidrogen|H<sup>+</sup>]] diletupkan dengan [[daya]] sebesar 635 [[watt|meV]],<ref>{{en}} {{cite web
| url = http://www.ncbi.nlm.nih.gov/pubmed/14871119
| title = Electrostatic study of the proton pumping mechanism in bovine heart cytochrome C oxidase
| accessdate = 2010-11-15
| work = Department of Chemistry, University of California-Davis; Popović DM, Stuchebrukhov AA.
}}</ref> untuk 1 molekul O<sub>2</sub> pada [[pH]] sekitar 8, namun mekanisme peletupan tersebut lenyap pada pH sekitar 10,5.<ref>{{en}} {{cite web
| url = http://www.ncbi.nlm.nih.gov/pubmed/19344748
| title = Internal charge transfer in cytochrome c oxidase at a limited proton supply: proton pumping ceases at high pH
| accessdate = 2010-11-15
| work = Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University; Lepp H, Brzezinski P.
}}</ref>
== Pranala luar ==
* {{en}} [http://www.ncbi.nlm.nih.gov/pubmed/206463 Cytochrome c oxidase is not a proton pump]
* {{en}} [http://www.ncbi.nlm.nih.gov/pubmed/40546 The mechanism of transmembrane delta muH+ generation in mitochondria by cytochrome c oxidase]
== Rujukan ==
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