Melanin synthesis
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The document discusses melanin synthesis and albinism, explaining that skin color is influenced by various genetic and environmental factors and that melanin is produced in melanocytes using tyrosine. Albinism, characterized by a lack of melanin due to genetic conditions, can affect both eyes and skin, presenting symptoms such as white appearance and vision defects. The document also covers types of melanin, causes of melanotic macules, and the implications of albinism on sun exposure and potential limitations in activities.
Melanin synthesis
- 1. Melanin synthesis & Albinism Sharad Gautam Lecturer, Biochemistry
- 2. Melanin тАв Skin color is determined by the relative concentrations of black & red melanins тАв This is dependent on genetic and environmental factors тАв Moles: due to hyperpigmentation caused by the hyperactivity of melanocytes тАв White patches: due to localized absence or degeneration of melanocytes from the skin.
- 3. Melanin synthesis тАв Melanin is black pigment of skin, hair & eyes тАв Synthesis occurs in melanosomes present in melanocytes. тАв Tyrosine is the precursor of melanin and tyrosinase is the enzyme involved in itтАЩs formation тАв Melanochromes formed from tyrosine polymerizes to form melanin polymers
- 5. Melanin types яВЫ Eumelanin (┬аbrown & black), яВЫ Pheomelanin, and яВЫ Neuromelanin яВЫ Tyrosinase is a copper-containing enzyme that is present in melanocytes
- 6. Melanin types яВЫ Eumelanin: яВЫ black eumelanin in the absence of other pigments causes grey hair. яВЫ brown eumelanin in the absence of other pigments causes yellow (blond) color hair. яВЫ Pheomelanin: яВЫ imparts a pink to red hue, depending upon its concentration. яВЫ concentrated in the lips, nipples, glans penis, and vagina. яВЫ When small amount of brown eumelanin in hair mixed with red pheomelanin, the result is┬аred hair. яВЫ Neuromelanin: яВЫ dark polymer pigment produced in specific populations of catecholaminergic neurons┬аin the brain
- 7. Tyrosine DOPA Dopaquinone Leucodopachrome Cysteine 5,6-Dihydroxyindole Melanin red polymers Indole 5-6-quinone melanochrome Melanin black polymers Tyrosine hydroxylase Tyrosinase Tyrosinase
- 10. Albinism
- 11. History Balthazar Telez coined the term тАЬalbinoтАЭ, meaning white Negro, when he saw white African tribe members along the coast of West Africa. He and the other explorers thought they were seeing two different races of people
- 13. What is albinism? тАв Albinism is a group of genetic conditions that causes a lack of pigment- melanin. тАв It can effect only the eyes or both the eyes and skin. тАв Most types of albinism are inherited when an individual receives the albinism gene from both parents. тАв The exception is one type of ocular albinism, which is passed on from mothers to their sons.
- 14. Description тАв Inherited by one of several modes: тАв autosomal recessive, autosomal dominant, or Complete albinism тАв Affected people may appear to have white hair, skin & iris color. тАв They may have vision defects and photophobia. тАв Oculocutaneous albinism is most severe form resulting from a deficiency of tyrosinase activity, causing a total absence of pigment from the hair, eyes & skin
- 15. Defects яВЫ Tyrosinase enzyme deficiency or reduced activity яВЫ Mutation in Tyrosinase related protein (TRP- 1) gene яВЫ Recessive inheritance of OCA1 and OCA2
- 16. Symptoms тАв Absence of pigment from the hair, skin, or iris of eyes тАв Lighter than normal skin and hair or complete albinism тАв Most forms of complete albinism have some of the following possible symptoms: тАв Rapid eye movements тАв Strabismus (eyes not tracking properly) тАв Photophobia (avoidance of light because of discomfort) тАв Decreased visual acuity тАв Functional blindness
- 17. Alternate names яВЫ Hypopigmentation яВЫ Ocular Albinism яВЫ Oculocutaneous Albinism
- 18. Treatment яВЫ The skin and eyes must be protected from the sun. Sunglasses (UV protected) may relieve photophobia.
- 19. Prognosis яВЫAlbinism does not affect the expected lifespan. яВЫActivities may be limited by intolerance to the sun.
- 20. Melanotic macule яВЫ The melanotic macule is the mouth equivalent of a freckle or brown pigmented patch of the skin. яВЫ One-third of lesions occur on the vermilion border of the lower lip, along with the buccal mucosa, gingiva and palate. яВЫ One of every 1,000 adults Large brown macule of the soft palate
- 21. Causes of melanotic macule яВЫ Children: racial origin, no treatment required. яВЫ Adults: may be smoke-induced, drug- induced, hormone-induced or spontaneous (without cause), and яВЫ Biopsied to rule out malignant melanoma. яВЫ Some inherited diseases show brown pigmentation of the oral membranes.