melanin

melanin , water-insoluble polymer of various compounds derived from the amino acid tyrosine . It is one of two pigments found in human skin and hair and adds brown to skin color; the other pigment is carotene , 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 sunburn ; skin cancer ).

melanin Dark pigment found in the skin, hair, and parts of the eye. It helps protect skin from ultraviolet radiation from the Sun. The amount of melanin determines skin colour. Absence of melanin results in an albino.

melanin Brown pigment formed when phenolic compounds in cut fruit and vegetables are exposed to air and oxidized; also the brown and black pigments of skin and hair.