Incorporation and binding of estrogens into melanin: comparison of mushroom and mammalian tyrosinases.
The activities of mushroom and melanoma tyrosinases towards the estrogens were compared. While the fungal enzyme is capable of hydroxylating estradiol to the 2-hydroxy compound and to oxidize the latter to the quinone, the mammalian enzyme does not have this ability. With dopa as substrate and an estrogen present in the reaction mixture, both enzyme reactions yield melanin with the steroid firmly incorporated into the pigment, although with the mammalian enzyme the incorporation is small. The steroid appears to be incorporated by covalent linkage. It is suggested that the incorporation of estrogens into melanin produced by mammalian tyrosinase is via their oxidation by oxidized intermediates of the dopa to melanin transformation. Melanin itself may function as oxidant for the estrogens. Whole melanoma cells are capable of binding estrogens and incorporating small amounts into melanosomes. Similarly, fresh melanosomes in isolation can incorporate estrogens into their structure, presumably by covalent bonding to their melanin.
Jacobsohn
G M
GM
Department of Biological Chemistry, Hahnemann University, Philadelphia, PA 19102.
Jacobsohn
M K
MK
D000818:Animals; D001487:Basidiomycota / Q000201:enzymology*; D004958:Estradiol / Q000031:analogs & derivatives* / Q000378:metabolism*; D002393:Estrogens, Catechol / Q000378:metabolism; D005260:Female; D007700:Kinetics; D008543:Melanins / Q000378:metabolism*; D008544:Melanocytes / Q000201:enzymology*; D008546:Melanoma, Experimental / Q000201:enzymology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D014442:Monophenol Monooxygenase / Q000378:metabolism*
D002393:Estrogens, Catechol; D008543:Melanins; D004958:Estradiol; C001390:2-hydroxyestradiol; D014442:Monophenol Monooxygenase