Part:BBa_K4414006
TYR
Usage and Biology
Usage and Biology Tyrosinase（TYR） is a key enzyme in melanin synthesis that catalyzes the rate-limiting step of the reaction. By activating tyrosine kinase can increase the yield of melanin, forming melanin deposition . The melanogenesis process is initiated with the oxidation of L-tyrosine to dopaquinone (DQ) by TYR. The resulting quinone will serve as a substrate for the synthesis of eumelanin and pheomelanin(Hearing & Jiménez, 1987). The formation of DQ is a rate-limiting step in the melanin synthesis because remainder of the reaction sequence can proceed spontaneously at a physiological pH value(Halaban et al., 2002). After DQ formation, it undergoes intramolecular cyclization to produce indoline, leukodopachrome (cyclodopa). The redox exchange between leukodopachrome and DQ give rise to dopachrome and L-3,4-dihydroxyphenylalanine (L-DOPA), which is also a substrate for TYR and oxidized to DQ again by the enzyme. Dopachrome gradually decomposes to give dihydroxyindole (DHI) and dihydroxyindole-2-carboxylicacid (DHICA). The later process is catalyzed by TRP-2, now known as dopachrome tautomerase (DCT). Ultimately, these dihydroxyindoles (DHI and DHICA) are oxidized to eumelanin. TRP-1 is believed to catalyze the oxidation of DHICA to eumelanin. Alongside, DQ is converted to 5-S-cysteinyldopa or glutothionyldopa in the presence of cysteine or glutathione. Subsequent oxidation gives benzothiazine intermediates and finally to produce pheomelanin. Although three enzymes, TYR, TRP-1 and TRP-2 are involved in the melanogenesis pathway, tyrosinase is exclusively necessary for melanogenesis.(Pillaiyar et al., 2017)
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000COMPATIBLE WITH RFC[1000]
Fuctional Validation and result
We introduce the plasmid with TYR into the cells, where melanogen is produced as shown.
Figure 1: (Left)The blackening of HEK-293T cells at 24 h or 48 h post glucocorticoids treatment in microscope.(Right)The blackening of HEK-293T cells at 24 h or 48 h post glucocorticoids treatment under the naked eye.
Reference
1. Halaban, R., Patton, R. S., Cheng, E., Svedine, S., Trombetta, E. S., Wahl, M. L., Ariyan, S., & Hebert, D. N. (2002). Abnormal acidification of melanoma cells induces tyrosinase retention in the early secretory pathway. The Journal of Biological Chemistry, 277(17), 14821–14828. https://doi.org/10.1074/jbc.M111497200
2. Hearing, V. J., & Jiménez, M. (1987). Mammalian tyrosinase—The critical regulatory control point in melanocyte pigmentation. The International Journal of Biochemistry, 19(12), 1141–1147. https://doi.org/10.1016/0020-711x(87)90095-4
3. Pillaiyar, T., Manickam, M., & Namasivayam, V. (2017). Skin whitening agents: medicinal chemistry perspective of tyrosinase inhibitors. Journal of Enzyme Inhibition and Medicinal Chemistry, 32, 403 - 425.
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