Cytochromes (synonym: myohemmin, histohematic) - hemoproteins, the biological function of which is the electron transfer is made (in the process of tissue respiration) by reversible changes valence iron atoms forming part of heme (see Hemoglobin).
Depending on the configuration of the prosthetic group cytochromes are divided into four types (each of which in turn contains several types of cytochromes): cytochromes a, b, c, d. Corresponding prosthetic group: iron-formyl-porphyrin (heme a or kindred heme with formyl side chain); protogen (iron-protoporphyrin); substituted mesogen; iron-digidropiridina.
Restored cytochromes give a clear range with three absorption bands (a, t, y), characteristic for each type of cytochromes, designed to detect cytochromes spectrophotometric methods. Cytochromes found in all animal and plant cells, as well as in yeast and some optional anaerobes. The role of many of cytochromes in the body are still unknown, although some attribute of highly specialized functions. The most important function of cytochromes need to consider their relationship with the normal oxidation chain in the process of respiration most fabrics. Recognized in the present time is the location of cytochromes in the chain of carriers of electrons are:
b - c1 - s - a - and3 - About2.
Bacteria often there are separate components of a complete cytochrome system, inherent in animal and plant tissues; in some cases instead found other cytochromes, missing in the animal and plant organisms.
The main components of the cytochrome system is localized in the mitochondria. In microsomes animal cells found cytochrome b5; in vegetable microsomes - b3; in chloroplasts of plant - b6.
Cytochromes poorly soluble in water; their solubility increases in the processing of source material containing cytochromes, surface-active substances. Currently available data indicate that most of the energy of biological oxidation is released as a result of reactions catalyzed by cytochrome system.
Characteristics of some of cytochromes. Cytochrome c is obtained in the crystalline form. Molecular weight of 12,000. In the body is as free, water-soluble, state, and associated with cellular particles. Oxidized cytochrome C is restored chemicals, such as hydrosulfite and others In the tissues of the body recovery may come at the expense of enzymes called zitohromoksidasy. Are they to flavoprotein. There are two types: oxidizing OVER recovered (restored OVER-cytochrome C-reductase) and NADP restored (reduced NADP-cytochrome C-reductase).
Cytochrome a3 (cytochrome oxidase; cytochrome-C : O2-oxidoreductase; Warburg respiratory enzyme - enzyme-carrying electrons from cytochrome c O2. Contains copper. The question of independent existence of cytochromes a, and a3 is controversial. It is assumed that both connections are one and the same protein. Recently obtained data indicate that cytochrome oxidase, perhaps, consists of six units, two of which are equivalent to a cytochrome3and four - cytochrome a.
In histochemistry cytochrome oxidase is determined by Nadi-reactions:
alpha-naphthol + dimethyl-alpha-phenylenediamine + 4 cytochrome c spontaneously → indefinably blue + 4 cytochrome C (restored) cytochrome oxidase + oxygen → cytochrome c + H2o
The result is the emergence of a blue or blue-violet color.
Cm. also the biological Oxidation.