Cytochrome

Cytochromes (also: cytochromes, Greek chroma = color) are colored proteins ( chromoproteins ) (hence the name, which means " cytochrome " ) that contain heme as a prosthetic group and act as a redox mediator by the iron ion in the heme oxidation number changes. Cytochromes are distinguished according to the variant of the heme, which they contain, and by its light absorption spectrum.

They play a role in cellular respiration in photosynthesis and other biochemical processes, where they act as a carrier of electrons in redox reactions ( cofactor of oxidoreductases ). There are about 50 different types. Cytochromes are found in cell organelles such as mitochondria and chloroplasts. In addition, cytochromes occur in animals in brown adipose tissue. Cytochromes give it - along with numerous vessels - the adipose tissue its brown color.

History

The cytochromes were discovered in 1884 by McMunn. Only 40 years after the discovery of David Keilin could interpret the spectra of living cells than that of the three most important Cytochrome a, b and c.

Properties

Cytochromes have a prosthetic group or several heme molecules. The cytochromes differ in heme -type and apo surrounding the heme. According to its characteristic light absorption spectra of a distinction is cytochrome a, b, c, and d

Examples

The best-studied cytochrome is cytochrome c, which is obtained from the cardiac muscle tissue of tuna or horses. It consists of about 100 amino acids and the molecular structure is well characterized by protein crystallography. Cytochrome c is evolutionarily a very old protein.

Unlike many other cytochromes, who undertake tasks in electron transport, are cytochrome P450 proteins and cyclooxygenase enzymes, generally oxygenases.