マッシュルームおよび黒緑豆（Ｍｕｎｇ　ｂｅａｎ）由来ポリフェノールオキシダーゼによるジフェノール化合物生成

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  • Production of Diphenols by Polyphenol Oxidase from Mushroom and Mung Bean (Vigna mungo).
  • マッシュルーム オヨビ クロリョクトウ Mung bean ユライ ポリフェノ

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Polyphenol oxidase (PPO) shows two different enzyme activities in vitro. One is oxidase activity and the other is hydroxylase activity. PPO oxidizes various o-diphenols to o-quinones in the absence of an electron donor, while it hydroxylates various monophenols to diphenols in the presence of an electron donor such as L-ascorbic acid. This paper deals with hydroxylation of monophenols by PPO (tyrosinase from mushroom and mung bean, Vigna mungo) in a special reference to electron donor requirement. The enzyme and the substrates (monophenols) were incubated in an assay mixture either without or with an electron donor at 30°C for various times (until 10min.). After incubation, the reaction was stopped by adding HCl, and then the reaction mixture was subjected to HPLC. The amount of hydroxylated substrate was determined by the decrease of substrate on the chromatograms. PPO required an electron donor for hydroxylation of p-coumaric acid but not for hydroxylation of L-tyrosine. Hydroxylation of L-tyrosine was not stimulated by the addition of the electron donors tested. These results suggested that the amino group in L-tyrosine may function as an electron donor. This assumption was supported by the following two experimental results. First, hydroxylation of p-coumaric acid was stimulated by addition of amino group-containing compounds. Secondly, p-hydroxyphenylpyruvic acid which has a structure of amino group-eliminated L-tyrosine, behaved as p-coumaric acid in hydroxylation by tyrosinase.

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