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标题：Umbelliferone and Esculetin: Inhibitors or Substrates for Polyphenol Oxidases?
本地全文：下载
作者：Francesca Sollai ; Paolo Zucca ; Enrico Sanjust 等
期刊名称：Biological and Pharmaceutical Bulletin
印刷版ISSN：0918-6158
电子版ISSN：1347-5215
出版年度：2008
卷号：31
期号：12
页码：2187-2193
DOI：10.1248/bpb.31.2187
出版社：The Pharmaceutical Society of Japan
摘要：Recently, an interesting debate arose about the nature (substrate versus inhibitor) of esculetin, a coumarin derivative, for mushroom polyphenol oxidase (PPO). The present study examined the behavior of PPOs preparations from fungal and plant origin towards esculetin as a substrate. Both enzymes were able to oxidize esculetin though at a slow rate. A higher sensitivity was reached when the assay was performed in the presence of 3-methyl-2-benzothiazolinone hydrazone (MBTH) even with a lower amount of PPO. These observations unambiguously confirmed that esculetin has to be considered a substrate for mushroom polyphenol oxidase. The oxidation of esculetin was also demonstrated for the first time by a fungal laccase. This should be taken into account because some mushroom PPO preparations could exert contaminant laccase activity. In addition, a PPO preparation from Ferula communis was demonstrated to use esculetin as a substrate. Umbelliferone, the monophenolic precursor of esculetin along the phenylpropanoid pathway, behaved as a competitive inhibitor for the monophenolase activity of mushroom PPO with a K _i value=0.014 m M . This is worth a mention because only a few couples of mono- and corresponding o -diphenol show such opposite behavior towards PPO. A possible role of PPO in the esculetin fate along biosynthesis pathway of coumarin derivatives is also discussed.
关键词：polyphenol oxidase;tyrosinase;laccase;esculetin;umbelliferone;Ferula communis