Melanin (MLN)
Melanin (MLN): Definition, Function, and Importance
What is Melanin?
Melanin (MLN) is a natural pigment responsible for the coloration of human skin, hair, and eyes. It is produced by specialized cells called melanocytes, primarily located in the basal layer of the epidermis. Melanin exists mainly in two forms:
- Eumelanin: Dark brown to black pigment, predominates in darker skin tones and provides effective protection against ultraviolet (UV) radiation.
- Pheomelanin: Yellow to red pigment, more abundant in lighter skin and red hair, less protective against UV damage.
Function of Melanin
- Skin Pigmentation: Melanin determines the wide spectrum of skin tones by varying in quantity, type, distribution, and melanosome density.
- Photoprotection: Melanin absorbs and dissipates over 99.9% of harmful UV radiation (UVA, UVB, and UVC), protecting skin cell DNA from damage and reducing the risk of skin cancers.
- Reactive Oxygen Species Scavenging: Melanin acts as an antioxidant neutralizing reactive oxygen species (ROS) generated by UV exposure, minimizing oxidative cellular damage.
- Pigmentation of Hair and Eyes: Melanin contributes to hair color and eye color, with different ratios of eumelanin and pheomelanin.
Melanin Biosynthesis
- Synthesized within melanocytes via a complex biochemical process involving the enzyme tyrosinase, which converts tyrosine to dopaquinone, leading to eumelanin and pheomelanin production.
- Melanosomes containing melanin are transferred to neighboring keratinocytes, dispersing pigment throughout the epidermis.
- Variations in melanocyte activity, melanin type, and melanosome size and distribution account for differences in skin color and UV sensitivity.
Clinical and Biological Significance
- Higher melanin levels confer greater natural protection against sunburn and skin cancers but may predispose to certain pigmentary disorders.
- Deficient melanin production causes conditions like albinism, characterized by pale skin, visual impairment, and extreme sun sensitivity.
- Melanin also colors specialized anatomical features such as lips, nipples, and genitalia.
Summary
Melanin is a crucial pigment that not only defines human coloration but plays a vital role in protecting skin from UV-induced damage by absorbing harmful radiation and neutralizing free radicals. Its balance and distribution underlie skin phototypes and influence susceptibility to various skin conditions.
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References:
Kobayashi T, Watanabe H, Matsuoka S. The Significance of Melanin Distribution in Human Skin. Scientific Reports. 2024;14(1):15762. DOI: 10.1038/s41598-024-53941-0. Available at: https://www.nature.com/articles/s41598-024-53941-0
