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 ?
In both cases, the researchers added melanin to the lysate to make it more light absorbent.
Melanin is produced naturally, but its production is also stimulated by exposure to the sun.
Green eyes, however, have far less melanin at the back of the iris and they also have some yellow pigment at the front.
Your skin normally produces the pigment melanin in specialized cells called melanocytes to mitigate the skin aging effects of the sun.
Melanocytes express estrogen receptors and estradiol increases the level of TRP-2, which stimulates melanocytes to produce melanin.
Extending this analogy, melanin can serve as a kind of 'electron bucket' at a certain level.
At week 10, melanin indices were significantly lower on the glutathione-treated side.
As a result, melanocytes are stimulated to overproduce melanin, and the excess melanin is unevenly distributed in the epidermis, causing hyperpigmentation (Matt et al.
The melanin content of their skin decreased giving them the fairer and white skin.
Hair greying is caused by an absence of melanin in hair so researchers want to find out IRF4's role in this process.
But if we look at the skin closely, the type, amount, and distribution of melanin in melanocytes (cells where melanin is made) and its interaction with keratinocytes (that produce certain signals that regulate the amount of melanin to be distributed), are the primary indicators of skin color, and once their behavior changes, the color of the skin changes, too.