Biochemistry of Brown

We are 50% of the way there and halfway through the campaign! Thank you everyone for your donations to date! 

Now this note may be a little more technical than most of you care for but it is interesting to understand the biochemistry the different eumelanin types to see the differences between black and brown. 

There are two types of melanins involved with pigmentation: eumelanin (black/brown) & phaeomelanin (red/yellow). This project is focused on determining the genetic cause for the difference between black & brown eumelanin. Phaeomelanin is formed from a slightly different pathway with the addition of the amino acid cysteine. 

It's known that eumelanin is formed from the oxidation of tyrosine through the actions of several enzymes including tyrosinase and late in the pathway by tyrosinase related protein 1 (TYRP1), the gene we plan on sequencing. Below is a figure showing the difference between the black & brown eumelanin forms (if I drew the chemical structures correctly! It's been a while since chemistry). The only difference between the polymers is a Carboxyl group (-COOH ). These polymers will then be oxidized further to form the final versions of eumelanin. 

 

For more detail check out the papers listed below, the second review listed should be open access. 

References & Further Reading for those interested: 

Ito, S. and Wakamatsu, K. (2011), Human hair melanins: what we have learned and have not learned from mouse coat color pigmentation. Pigment Cell & Melanoma Research, 24: 63–74. doi:10.1111/j.1755-148X.2010.00755.x

Micillo, R et al. "Fifty Shades" of Black and Red or How Carboxyl Groups Fine Tune Eumelanin and Pheomelanin Properties. Int. J. Mol. Sci. 2016, 17(5), 746; doi:10.3390/ijms17050746