Cytochrome Oxidase

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cytochrome oxidase

[′sīd·ə‚krōm ′äk·sə‚dās]
Any of a family of respiratory pigments that react directly with oxygen in the reduced state. Also known as cytochrome a3.

Cytochrome Oxidase


(also cytochrome a3), an enzyme of the oxido-reductase class; the final component of the chain of respiratory enzymes that carry electrons from the cytochrome c to molecular oxygen. Cytochrome oxidase was discovered in 1926 by the German scientist O. Warburg (Warburg’s respiratory enzyme). In plant and animal cells, it is localized on the inner membrane of mitochrondria. Chemically, it is a complex protein, whose molecule consists of two hemes, two copper atoms, and 20–30 percent lipid constituent. Both hemes are heme a; however, only part of the heme a is oxidized, and it is designated a3. It is still unclear whether cytochrome oxidase is a single protein with two functionally different forms of heme, or whether it is a complex of two different cytochromes. Copper is bound to the protein by a sulfur-containing ligand. When the copper is separated from the protein, cytochrome oxidase becomes inactive.

The molecular weight of cytochrome oxidase varies, according to different data, from 50,000 to 240,000. Cyanide, azide, CO, and hydroxylamine are cytochrome oxidase inhibitors.


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As indicated previously, cytochrome C oxidase chain I mRNA was unchanged in the tadpole diencephalon.
These included plectin, an intermediate filament-binding protein that provides mechanical strength and structural integrity to the cytoskeleton (49); NAP4, implicated in coordinating various signaling pathways including growth factor and cell adhesion receptors (50); BAI2 and BAI3, membrane proteins that inhibit neovascularization and act as growth suppressors of glioblastoma (primary brain tumor development) (51); arcadlin, a novel cadherin molecule expressed at the synapses that may play an important role in activity-induced synaptic reorganization underlying long-term memory (52); cytochrome C oxidase chain I, an important mitochondrial proton-pumping respiratory protein; and NADH dehydrogenase subunit 4, involved in glycolosis and cellular respiration.
in mtDNA that encode for two subunits or cytochrome c oxidase (COI and
Valproate-induced hepatic failure in a case of cytochrome c oxidase deficiency.