| cytochrome | <biochemistry> Any electron transfer haemoprotein having a mode of action in which the transfer of a single electron is effected by a reversible valence change of the central iron atom of the haem prosthetic group between the +2 and +3 oxidation states. Classified as cytochromes a in which the haem contains a formyl side chain, cytochromes b, which contain protohaem or a closely similar haem that is not covalently bound to the protein, cytochromes C in which protohaem or other haem is covalently bound to the protein and cytochromes d in which the iron tetrapyrrole has fewer conjugated double bonds than the haems have. Well known cytochromes have been numbered consecutively within groups and are designated by subscripts (beginning with no subscript), for example cytochromes C, c1, C2,. New cytochromes are named according to the wavelength in nanometres of the absorption maximum of the a band of the iron (II) form in pyridine, for example, C 555. Origin: Gr. Chroma = colour (18 Nov 1997) |
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| cytochrome a | <chemical> Cytochromes (electron-transporting proteins) in which the haem prosthetic group is haem a, i.e., the iron chelate of cytoporphyrin ix. Chemical name: Cytochrome a (12 Dec 1998) |
| cytochrome aa3 | <enzyme> An enzyme complex of the inner mitochondrial membrane that catalyses the reaction between ferrocytochrome c and oxygen to yield ferricytochrome c and water. It is associated with the pumping of protons and the resultant phosphorylation of ADP to ATP. The reaction is the terminal event in the electron transport scheme by which oxygen is used for fuel combustion. It is a part of Complex IV of the respiratory chain. A deficiency of one or more of the polypeptides of this complex results in neuronal loss in brain leading to psychomotor retardation and neurodegenerative disease. Synonym: cytochrome aa3, indophenol oxidase, indophenolase. Chemical name: Ferricytochrome-c:oxygen oxidoreductase Registry number: EC 1.9.3.1 (12 Dec 1998) |
| cytochrome b | <chemical> Cytochromes (electron-transporting proteins) with protoheme or a related haem as the prosthetic group. The prosthetic group is not covalently bound to the protein moiety. Chemical name: Cytochrome b (12 Dec 1998) |
| cytochrome b(5) reductase | <enzyme> May be the enzyme for methemoglobin reductase activity Registry number: EC 1.6.2.2 Synonym: NADH-cytochrome b5 reductase, mcr1 protein, saccharomyces cerevisiae, mcr1 gene product (26 Jun 1999) |
| cytochrome b5 | <chemical> A cytochrome occurring in the endoplasmic reticulum that acts as an intermediate electron carrier in some reactions catalyzed by mixed function oxidases, e.g., fatty acid desaturation. It further activates molecular oxygen for an attack on the substrate. Mw 16kda. Chemical name: Cytochrome b5 (12 Dec 1998) |
| cytochrome b5 reductase | <enzyme> An enzyme catalyzing the reduction of 2ferricytochrome b5 to 2ferrocytochrome b5 at the expense of NADH; has a role in fatty acid desaturation; a deficiency can lead to hereditary methemoglobinaemia (type I, only observed in erythrocyte cytosol; type II, deficiency in all tissues; type III, deficiency in all haematopoetic cells). (05 Mar 2000) |
| cytochrome C | A type of cytochrome, a protein which carries electrons, that is central to the process of respiration in mitochondria (an organelle found in eukaryotes which produces energy). (09 Oct 1997) |
| cytochrome C hydrolase | <enzyme> From yeast mitochondrial inner membrane Registry number: EC 3.4.- (26 Jun 1999) |
| cytochrome C methyltransferase | <enzyme> From crithida oncopelti Registry number: EC 2.1.1.- (26 Jun 1999) |
| cytochrome c reductase | <enzyme> A flavoprotein containing iron. Cytochrome c may act as receptor. The enzyme reversibly catalyses the oxidation of NADH to NAD and reduced acceptor. An inherited deficiency of this complex results in overwhelming acidosis. Synonym: cytochrome c reductase. Chemical name: NADH:(acceptor) oxidoreductase Registry number: EC 1.6.99.3 (12 Dec 1998) |
| cytochrome C synthetase | <enzyme> Forms cytochrome c from the apoprotein + hemin, requires NADPH; mechanism not given 9/81 Registry number: EC 4.99.- Synonym: cytochrome c haem lyase, hccs gene product (26 Jun 1999) |
| cytochrome C-methionine methyltransferase | <enzyme> Forms s-methylmethionine Registry number: EC 2.1.1.- Synonym: cyt c-met methyltransferase (26 Jun 1999) |
| cytochrome c1 | <chemical> The 30-kD membrane-bound c-type protein of mitochondria that functions as an electron donor to cytochrome c in the mitochondrial and bacterial respiratory chain. Chemical name: Cytochrome c1 (12 Dec 1998) |
| cytochrome C1 haem lyase | <enzyme> A mitochondrial haem lyase from saccharomyces cerevisiae; mw about 31 kD; facilitates covalent attachment of haem to the apoforms of c-type cytochromes Registry number: EC 4.99.- Synonym: yeast cc1hl (26 Jun 1999) |