is generated, which is an intermediate that leads to the final synthesis step of melanin production. Melanins
are heterogenous metabolites that arise from polyphenolic compounds; these are attained from the oxidative
condensation of amino acid L-tyrosine via the enzyme reaction that includes tyrosinase (Ito et al., 2011).
Two types of melanin that can be produced via this synthesis process; the first is black- brown eumelanin; this
is the primary type of melanin found in individuals with dark skin. The second type is yellow-red pheomelanin,
which is found in individuals with fairer skin and is responsible for producing yellow and brown pigmentation
(Polidori et al., 2017). Therefore, other skin tones are considered as a combination of the various pigments
(Rawlings, 2006). This, therefore, means that the differences observed in skin colour are as a result of the
amount and type of melanin being produced, this is further emphasised in figure II (Ito et al., 2011; Polidori et
al., 2017).
Figure II: This figure was adapted from Brenner and Hearing, 2007.
Figure II demonstrates the amount of melanin present in Caucasian, Asian, and Black skin. As seen from the
images, Black skin produces more melanin by melanocytes in the basal layer in comparison to Caucasian
and Asian skin. They found that the quantity of melanocytes cells is similar amongst all three ethnic groups;
however, it is the amount of melanin being produced by the melanocytes that bring about diversity.
It has been suggested that the melanosomes found in light skin individuals are smaller and are mostly in their
early stage of maturation. Compared to dark skin individuals that have larger melanosomes and are found
to be more matured; this is illustrated in figure III. The melanosomes have a maturation process known as
melanogenesis, involving multiple steps. During the first stage, a vesicle is developed and is ensembled inside a
fibrillar matrix formed by two glycoproteins Pmel17 and MART-1.
The incorporation of the vesicles with tyrosinase and other melanogenesis enzymes form stage two. In stage
three, the melanosomes start producing melanin, which is then polymerised, the polymerisation enables
the melanin to settle on the internal fibrils. Stage four is the final stage whereby the melanin has matured;
different types of melanin can then be synthesised in separate melanosomes (Cichorek et al., 2013). Studies
have suggested that melanosomes of East Indians, Japanese, Mongoloids, Chinese and European-American
Caucasians are more clustered together in two or more complexes in contrast to Australian aborigines and
Africans that have individually dispersed melanosomes (Rawling, 2006). This could, therefore, explain why
individuals with lighter skin tones are more prone to certain types of skin cancers when compared to other
groups due to the differences in the size and the maturation stage of the melanosomes.
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