MadSci Network: Medicine

Re: More questions on melanin drugs for tanning

Date: Wed Jun 7 16:49:43 2000
Posted By: Mike Crawford, Postdoctoral Fellow, Biology
Area of science: Medicine
ID: 958065366.Me

Greetings Michael--

Get ready for probably too much information.

Statements on those dietary supplements can apply to anything:
The average U.S. diet may not include dozens of vitamins/minerals/amino acids that are important
for the production of melanin and thousands of other things.  If you were to ask 
specifically what compound it is, they would probably say tyrosine or something like that.

There doesn't appear to be an exact molecular structure of melanin--probably because it is an 'irregular' molecule (it doesn't always have the same overall shape or 

DEFINITION: a high molecular weight pigmented irregular biopolymer consisting of indole rings derived from the amino acid tyrosine  with intermediates of L-dopa, 
dopamine and various analogs.

Some of the proteins involved in the mammalian production of melanin found through mouse 'albino' mutants and other pigment mutants are:
tyrosinase (catalyzing the most critical first step from tyrosine to melanin)
tyrosinase-related protein 1
tyrosinase-related protein 2
tyrosine hydroxylase
melanosomal tyrosine transporter

Most of the production of melanin is in skin cells (not surprising) in a specialized structure called the 'melanosome', but it can also be synthesized in neurons as well by an 
unclear mechanism.  Melanogenesis is regulated by UV irradiation, which leads to DNA damgage and subsequent hormone production, the melanocyte stimulating hormone

Here are a couple of articles that maybe you can look into at your school library. 
Maybe they have structure pictures:

Int J Biochem Cell Biol 1997 Nov;29(11):1235-9
Riley PA 
Department of Molecular Pathology, University College London Medical School, U.K.

Melanin is an irregular light-absorbing polymer containing indoles and other intermediate products derived from the oxidation of tyrosine. Melanin is widely dispersed in the 
animal and plant kingdoms. It is the major pigment present in the surface structures of vertebrates. The critical step in melanin biogenesis is the oxidation of tyrosine by the 
enzyme tyrosinase. In vertebrates this enzyme is active only in specialized organelles in retinal pigment epithelium and melanocytes. In mammals melanin is formed as 
intracellular granules. Melanin granules are transferred from
melanocytes to epithelial cells and form the predominant pigment of hair and epidermis. Melanin has many biological functions. Reactive quinone intermediates in the 
melanin biosynthetic pathway exhibit antibiotic properties and the polymer is an important strengthening element of plant cell walls and insect cuticle. Light absorption by 
melanin has several biological functions, including photoreceptor shielding, thermoregulation, photoprotection, camouflage and display. Melanin is a powerful cation 
chelator and may act as a free radical sink. Melanin is used commercially as a component of photoprotective creams, although mainly for its free radical scavenging rather 
than its light absorption properties. The pigment is also a potential target for anti-melanoma therapy.

FASEB J 1991 Nov;5(14):2902-9
Enzymatic control of pigmentation in mammals. 
Hearing VJ, Tsukamoto K
Laboratory of Cell Biology, National Cancer Institute, Bethesda, Maryland 20892.

Visible pigmentation in mammals results from the synthesis and distribution of melanin in the skin, hair bulbs, and eyes.  The melanins are produced in melanocytes and 
can be of two basic types: eumelanins, which are brown or black, and phaseomelanins, which are red or yellow. In mammals typically there are mixtures of both types. 
The most essential enzyme in this melanin biosynthetic pathway is tyrosinase and it is the only enzyme absolutely required for melanin
production. However, recent studies have shown that mammalian melanogenesis is not regulated solely by tyrosinase at the enzymatic level, and have identified additional 
melanogenic factors that can modulate pigmentation in either a positive or negative fashion. In addition, other pigment-specific genes that are related to tyrosinase have 
been cloned which encode proteins that apparently work together at the catalytic level to specify the quantity and quality of the melanins synthesized. Future research 
should provide a greater understanding of the enzymatic interactions, processing, and tissue specificity that are important to pigmentation in mammals.

I got most of this answer from MEDLINE--you may want to check it out:

MEDLINE is an online database of all literature pertaining to
topics in medicine and the biological sciences. You can search
for resources and articles via the many WWW interfaces, including:


Hope this helps.
Mike Crawford, Admin MadSci Network

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