Quantitative analysis of eumelanin and pheomelanin
in humans, mice, and other animals: a comparative review.
homochromy, crypsis, color change, image analysis, habitat choice, pheomelanin
As outlined above, melanin itself provides protection against reactive oxygen species and toxic free radicals; but, on the other hand, the process of melanin biosynthesis itself, particularly that of pheomelanin
, has the capacity to generate reactive oxygen species that may cause DNA damage; and intermediates of melanin biosynthesis such as quinones and semiquinones are potentially mutagenic and as such can promote cytogenetic instability.
SOURCE: Q.LI ET AL/SCIENCE 2012 Pigment Eumelanin Pheomelanin
Mixed Mixed Melanosome shape Found in Red- Tufted Double- Microraptor winged titmouse crested blackbird cormorant
Importantly, it is known that the melanogenetic pathway is shifted from eumelanin toward pheomelanin
formation when GSH or cysteine is added to melanocytes or melanoma cell lines.
coat colour dilution in French cattle breeds is not correlated with the TYR TYRP1 and DCT transcription levels.
In the reaction, tyrosine is first oxidized to dopaquinone, which either cyclises to give a dihydroxyindole precursor of black or brownish eumelanins or reacts with cysteine to give a precursor of reddish brown pheomelanin
They determine the phenotype of our skin and hair by producing black, brown eumelanin or yellow, red pheomelanin
[alpha]-MSH also regulates pigment production and deposition through activation of tyrosinase, the enzyme that catalyzes synthesis of dopaquinone, the first step in melanogenesis ; in turn, dopaquinone reacts with intracellular cystine (supplied by the cystine/glutamate transporter, xCT) to produce cysteinyl-dopa, a rate-limiting step in the synthesis of pheomelanin
during inflammation .
Melanocytes produce two forms of melanin, black-brown eumelanin and red-yellow pheomelanin
. Skin and hair colour is determined by the total amount and ratio of eumelanin to pheomelanin
Another form of melanin is pheomelanin
, a cysteine containing red-brown polymer of benzothiazine units largely responsible for red hair and freckles.
Red hair is caused by a recessive gene on chromosome 16 and has high levels of pigment pheomelanin
. The MC1R variant gene is also linked to freckles.