The melanins are major organic pigments responsible for the color of theintegument in the animal kingdom. In humans, the color of the skin , the hair andeyes are dependent primarily on its type and its concentration. Many animals also occur, including birds (coloring feathers ), many fungi, and some protozoans .
Biological melanins are macromolecules produced mostly by the melanocytes , by addition or condensation of monomers formed from tyrosine ( eumelanin ) or tyrosine and cysteine ( pheomelanin ), with the help of the enzyme tyrosinase . A small proportion, as the neuromelanin of the substantia nigra of the human brain is not made in melanocytes but is probably the metabolism of amine easy asdopamine .
There are also artificial melanins: polyacetylenes , polyanilines , and polypyrroleblack or brown, and their copolymers , and they have an industrial or biotechnological application.
The main role of melanin is the pigment protection against radiation UV . In some animals, the melanophores, chromatophores holders melanin contribute to camouflage or report their transformations emotion, stress or a change in the environment (temperature, etc..). Some invertebrates, pathogens are encapsulated in melanin, which thus help home defense against infections. It also appears that its carboxylate groups and phenol hydroxyl medium can isolate some harmful components when in excess, such as heavy metals
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