メラニン色素の生合成と崩壊

概要

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The mechanism of melanogenesis in melanin-forming cells and degradation of melanosomes in epidermal keratinocytes was discussed. Epidermal melanocytes are unicellular, secretory, exocrine glands that elaborate melanosomes in much the same way as the pancreatic exocrine glands produce zymogen granules. The melanin-pigment-synthesizing enzyme, tyrosinase, is synthesized on the ribosomes, and then transferred via the cisternae of the endoplasmic reticulum to the Golgi sac, where, probably, tyrosinase is assembled into units, each of which is surrounded by a limiting membrane. This organelle is the first stage in the development of the melanosomes. Melanization is carried out and completed in the melanosomes. Full-melanized mature melanosomes, under the normal condition, are transferred from melanocytes to keratinocytes probably by active participation of keratinocytes. Melanosomes are present in melanocytes mainly as discrete particles, but, in keratinocytes, they occur as aggregate of three or more particles within membrane-delimited organelles, known as "melanosome complexes", which showed positive acid phosphatase activity. Melanosomes engulfed by the epidermal keratinocytes appear to undergo gradual degradation, and most become fragmented into small dense particles.
北里大学の論文
1971-08-30