melanin

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Related to Pheomelanin: Eumelanin

melanin

(mĕl`ənĭn), water-insoluble polymer of various compounds derived from the amino acid tyrosinetyrosine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein.
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. It is one of two pigments found in human skin and hair and adds brown to skin color; the other pigment is carotenecarotene
, long-chained, unsaturated hydrocarbon found as a pigment in many higher plants, particularly carrots, sweet potatoes, and leafy vegetables. Carotene is thought to assist in trapping light energy for photosynthesis or to aid in chemical reduction.
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, which contributes yellow coloring. The synthesis of melanin reactions is catalyzed by the enzyme tyrosinase; an inherited lack of tyrosinase activity results in one of the forms of albinism. Tyrosinase is found in only one specialized type of cell, the melanocyte, and in this cell melanin is found in membrane-bound bodies called melanosomes. Melanosomes can be transferred from their site of synthesis in the melanocytes to other cell types. The various hues and degrees of pigmentation found in the skin of human beings are directly related to the number, size, and distribution of melanosomes within the melanocytes and other cells. Besides it role in pigmentation, melanin, which absorbs ultraviolet light, plays a protective role when skin is exposed to the damaging rays of the sun (see sunburnsunburn,
inflammation of the skin caused by actinic rays from the sun or artificial sources. Moderate exposure to ultraviolet radiation is followed by a red blush, but severe exposure may result in blisters, pain, and constitutional symptoms.
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; skin cancerskin cancer,
malignant tumor of the skin. The most common types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Rarer forms include mycosis fungoides (a type of lymphoma) and Kaposi's sarcoma.
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).

melanin

[′mel·ə·nən]
(biochemistry)
Any of a group of brown or black pigments occurring in plants and animals.

melanin

any of a group of black or dark brown pigments present in the hair, skin, and eyes of man and animals: produced in excess in certain skin diseases and in melanomas
References in periodicals archive ?
Dysplastic melanocytic nevi contain high levels of pheomelanin: quantitative comparison of pheomelanin/ eumelanin levels between normal skin, common nevi, and dysplastic nevi.
The reddish color displayed by azure sand grasshoppers has recently been reported to be related to the presence of pheomelanin, a pigment formerly thought to be restricted to vertebrates only.
Lamoreux et al., "Slc7a11 gene controls production of pheomelanin pigment and proliferation of cultured cells," Proceedings of the National Academy of Sciences of the United States of America, vol.
Pheomelanin, that is responsible for red hair and freckles in humans and orange and chestnut coloration in other animals, is known to increase the damage to skin cells and melanoma risk when present in large amounts.
Since all melanin-based color is formed by a combination of two melanin pigments, eumelanin (which makes dark colors) and pheomelanin (which makes yellow to red colors), they speculated that eumelanin may be more susceptible to degradation than pheomelanin pigments, which overtime could lead to reduced proportion soft his pigment in the feathers, ultimately resulting in higher reflectance at longer wavelengths (i.e., giving the feathers a slightly reddish color).
Melanin is the substance that gives skin, hair and eyes their colour, dependent on the relative amounts of the two forms of melanin, eumelanin and pheomelanin. People who produce mostly eumelanin tend to have brown or black hair; those who produce mostly pheomelanin tend to have red or blond hair (4,5).
Redheads have more of another pigment called pheomelanin.
Melanins are classified in: Allomelanin (Allo) present in plants and fungi, Neuromelanin (Neu) present in nervous cell, Pheomelanin (Pheo) and Eumelanin (Eu) that can be found in the skin, hair and iris.
The sulfur content of the amino acids cysteine and methionine promotes the abundance of the lighter-skin pigment pheomelanin. Thienna discovers that the first humans were black; but sulfur-rich lower-toxin diets lightened the skin of early agricultural peoples.
The presence of some MC1R variants fails to shift the production from red/yellow pigment (pheomelanin) to black/brown pigment (eumelanin), causing less efficient protection against ultraviolet radiation.
Specimens captured in the different localities presented the following characteristics with respect to the fur coat and coloration: the dorsum had short guard hairs (9-10 mm), with a yellowish pheomelanin portion, giving the back an agouti colour.