|MadSci Network: Medicine|
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 architecture). 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 Melanin. 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: PUBMED: http://www.ncbi.nlm.nih.gov/PubMed/ ENTREZ: http://www4.ncbi.nlm.nih.gov/Entrez/basic.html Hope this helps. Mike Crawford, Admin MadSci Network
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