Cytochromes (from kyto -, Greek = cell and chroma = color = cell dye) are a group of highly conserved, colored proteins (chromoproteins) that contain an iron-containing heme group. They are found in cell organelles such as mitochondria and chloroplasts in all animals, plants, in all aerobic and most anaerobic microorganisms.
Cytochromes have a central function as electron carriers in the respiratory chain and photosynthesis.
In addition, cytochromes are found in animals in the brown fatty tissue. The cytochromes - together with numerous vessels - give the fatty tissue its brown colour.
Cytochromes form a subgroup of haemoproteins (haem consists of an iron ion complexed by a ring-shaped chelate ligand, porphyrin), to which haemoglobins and myoglobins also belong.
The individual cytochromes (there are about 50 different types) are divided into the 3 main groups a, b and c according to their chemical structure.
Cytochrome P-450is a mitochondrial oxygenase found in the liver and catalyses the oxidation of organic compounds by oxygen. Cytochrome P-450 (the name comes from its absorption band at 450 nm) occurs in many different forms (isoenzymes) and is responsible, among other things, for hydroxylation reactions of steroids. It is also involved in the degradation of many pharmaceuticals (detoxification function).