Phäomelanin

Phäomelanin is a type of melanin pigment found in vertebrates. Unlike eumelanin, the other major type of melanin, phäomelanin produces reddish-yellow to brown colors. It is responsible for the red hair color in humans and the yellow or reddish hues seen in the fur of many animals, such as foxes, squirrels, and some dog breeds.

The synthesis of phäomelanin begins with the amino acid tyrosine, just like eumelanin. However, at a certain point in the biosynthetic pathway, a reaction involving cysteine leads to the formation of benzothiazine intermediates, which are characteristic of phäomelanin. This chemical difference results in its distinct color properties and less protective capabilities compared to eumelanin.

The amount and distribution of phäomelanin, often in combination with eumelanin, determine the specific coloration of an organism. Variations in the genes that regulate melanin production, particularly genes like MC1R (melanocortin 1 receptor), play a significant role in the relative proportions of phäomelanin and eumelanin produced. Individuals with mutations in MC1R often have higher levels of phäomelanin, leading to lighter hair and skin tones and increased susceptibility to UV radiation.

While phäomelanin contributes to the visual appearance of many species, it is generally considered to offer less protection against the damaging effects of ultraviolet (UV) radiation than eumelanin. This is because phäomelanin is more prone to producing reactive oxygen species when exposed to UV light, which can cause cellular damage. Consequently, organisms with a higher proportion of phäomelanin may require additional protective mechanisms or exhibit behaviors that minimize sun exposure.