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Tirosinase: uma enzima para múltiplas abordagens
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A tirosinase (monofenol monooxigenase, EC 1.14.18.1) é a enzima que catalisa a hidroxilação de monofenóis e de difenóis a o-quinonas. Estruturalmente, a enzima é constituída por dois átomos de cobre no sítio ativo, estando cada um deles ligado a três histidinas. O mecanismo de ação da tirosinase é descrito através de dois ciclos catalíticos interligados, conforme o envolvimento da enzima na hidroxilação de monofenóis a o-difenóis ou na oxidação de o-difenóis a o-quinonas reativas, sendo estes ciclos o ciclo da monofenolase e o ciclo da difenolase, respetivamente.
A tirosinase está envolvida em processos como a produção de melanina e o escurecimento das plantas após colheita. Uma vez envolvida na produção de melanina, a enzima encontra-se associada a várias condições tais como melanoma, vitiligo e albinismo, podendo a sua inibição e/ou ativação ser a solução para estas doenças. Devido ao seu envolvimento no escurecimento das plantas após colheita, a tirosinase apresenta-se como uma enzima de interesse para a indústria alimentar, uma vez que a sua inibição pode aumentar a vida-útil destes alimentos. Além destas duas aplicações, a enzima é ainda estudada pela indústria para ser utilizada na produção de antioxidantes e fármacos, na formação de biopolímeros, no tratamento de resíduos contendo fenóis tóxicos e poluentes e na produção de biossensores. Estes biosenssores baseiam-se na inibição da tirosinase na presença de um substrato mono ou difenólico para a determinação de compostos que podem ir de pesticidas a fenóis do chá.
The tyrosinase (monophenol monooxigenase, EC 1.14.18.1 ) is the enzyme that catalyzes the hydroxylation of monophenols and diphenols to the corresponding o-quinones. Structurally, the enzyme is constituted by two atoms of copper in the active site, and each one of them is bind to three molecules of histidine. The mechanism of action of tyrosinase is described by means of two interconnected catalytic cycles, as the enzyme is involved in the hydroxylation of monophenols to o-diphenols or oxidation of diphenols to the reactive o-quinones, being these the monophenolase and diphenolase cycles, respectively. Tyrosinase is involved in processes such as the production of melanin and the post-harvest browning of plants. Once involved in the production of melanin, tyrosinase is associated with various conditions such as melanoma, vitiligo and albinism, and its inhibition and/or activation may be the solution for these diseases. Due to its involvement in post-harvest browning, tyrosinase presents itself as an enzyme of interest for the food industry, since its inhibition can increase the shelf life of these foods. In addition, the enzyme is still studied by industry to be used in the production of antioxidants and drugs, in the production of biopolymers, in treatment of samples containing phenols and toxic pollutants and in the production of biosensors. These biosenssores are based on the inhibition of tyrosinase in the presence of a mono- or diphenolic substrate for determination of compounds that can go from pesticides to the phenols of tea.
The tyrosinase (monophenol monooxigenase, EC 1.14.18.1 ) is the enzyme that catalyzes the hydroxylation of monophenols and diphenols to the corresponding o-quinones. Structurally, the enzyme is constituted by two atoms of copper in the active site, and each one of them is bind to three molecules of histidine. The mechanism of action of tyrosinase is described by means of two interconnected catalytic cycles, as the enzyme is involved in the hydroxylation of monophenols to o-diphenols or oxidation of diphenols to the reactive o-quinones, being these the monophenolase and diphenolase cycles, respectively. Tyrosinase is involved in processes such as the production of melanin and the post-harvest browning of plants. Once involved in the production of melanin, tyrosinase is associated with various conditions such as melanoma, vitiligo and albinism, and its inhibition and/or activation may be the solution for these diseases. Due to its involvement in post-harvest browning, tyrosinase presents itself as an enzyme of interest for the food industry, since its inhibition can increase the shelf life of these foods. In addition, the enzyme is still studied by industry to be used in the production of antioxidants and drugs, in the production of biopolymers, in treatment of samples containing phenols and toxic pollutants and in the production of biosensors. These biosenssores are based on the inhibition of tyrosinase in the presence of a mono- or diphenolic substrate for determination of compounds that can go from pesticides to the phenols of tea.
Descrição
Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, Universidade de Lisboa, Faculdade de Farmácia, 2015
Palavras-chave
Tirosinase Mecanismo ação tirosinase Monofenolase Difenolase Inibidores da tirosinase Melanina Escurecimento enzimático Indústria Biosenssores Mestrado Integrado - 2015