melanin

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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 ?
Hypermethylation in the genistein-supplemented population results in decreased ectopic Agouti expression, which reduces yellow phaeomelanin production and protects against adult-onset obesity.
There are two different types of melanin, eumelanin with black pigments and phaeomelanin with yellow pigments.
19) measured the amounts of eumelanin and phaeomelanin in hair from rodents given phencyclidine and related the incorporation of phencyclidine to the melanin content.
As a qualitative trait, the plumage colour of poultry is determined by the relative content and distribution of eumelanin and phaeomelanin produced in melanocytes.
Phaeomelanin is a reddish-brown to yellow pigment occurring in human and animal hair.
6] A reduced form of glutathione has a dual role in the depigmentation of colored skin: The mechanism of action may involve competitive binding with the color forming precursors of tyrosine (dopaquinone) to form less-colored phaeomelanin.
27) Eumelanin is brownish-black, and phaeomelanin reddish-yellow.