Melanin (/ˈmɛlənɪn/), also known as eumelanin, is a pigment that is produced by melanocytes in the skin of most mammals, including humans. It is responsible for the brown or black coloration of the skin, hair, and eyes. Melanin protects the body from damage by absorbing ultraviolet (UV) radiation from the sun.
There are two types of melanin: eumelanin and pheomelanin. Eumelanin is responsible for brown or black pigmentation, while pheomelanin produces yellow or red hues. The ratio of these two types of melanins present in an individual’s skin helps determine their natural skin color.
The production of melanin occurs when an enzyme called tyrosinase catalyzes the conversion of the amino acid tyrosine into dopaquinone. Dopaquinone is then converted into either eumelanin or pheomelanin depending on the presence of other enzymes and substrates.
Eumelanogenesis results in the production of eumelanin, which can be further subdivided into two types: brown eumelanin and black eumelanin. Brown eumelanins are generally more prevalent than black eumelanins. Black eumelananins are thought to provide better protection against UV radiation due to their higher absorption coefficient.
Pheomelaogenesis leads to the formation of pheomelin, a reddish-yellow pigment found in certain animals such as chickens and fish. Pheomelin can be broken down into two subtypes: red pheomelin and yellow pheomelin; however, only trace amounts of yellow pheomelin have been found in human beings.
The concentration and distribution of melanocytes within the epidermis determines an individual’s skin coloration patterns; for example, freckles are caused by localized areas with high densities of melanocytes producing large amounts of melanosomes (melanosome being a typeof cell organelle that contains melanins). The size, number,and maturityof these cells affect both hair and skin coloration.”