| Summary: | 碩士 === 國立暨南國際大學 === 生物醫學科技研究所 === 93 === Betanin, distributed in the flower of the plant, fruit and some advanced fungi, is water-soluble nitrogen pigment, and is potent to suppress tumor, lung cancer, and skin cancer. It can be applied to the food as a plant pigment source, which legally is a color-presenting garniture, and presently has widely been commercialized.
Melanin biosynthetic pathway exists in the insects, animals, and plants. In this pathway, tyrosinase hydroxylates tyrosine (monophenolase activation) to Dopa, and subsequently oxidizes Dopa to dopaquinone (diphenolase activation). Oxygen molecule is involved in both steps, followed by a series of nonenzymatic steps, leading to the formation of the melanin. Tyrosinase is the key in Melanin biosynthetic pathway. Tyrosinase (polyphenol oxidase; EC 1.14.18.1) is a copper-containing polypheonl oxygenase, widely distributed in the microorganisms, animals, and plants. It’s assorted into three types (oxy, deoxy, met form), and all of which interact with phenolic compounds. Emet and Eoxy are inactive and active to tyrosine respectively. The conversion of Emet to Eoxy causing lag time is the typical characteristic of monophenolase activity of tyrosinase. Also, Emet and Eoxy forms are active to diphenolase; therefore, diphenolase activity lacks lag time.
As betanin is employed in the reaction , the lag time can be shortened. Betanin reduces met form of tyrosinase (inactive to tyrosine) to deoxy form (that oxygen molecule can only react with), which binds to dioxygen to form oxy form. Betanin can activate monophenolase activity of tyrosinase, but not the diphenolase activity. Based on the result , betanin can be applied to enhance melanin biosynthesis.
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