Epithiospecifier Protein from Broccoli (Brassica oleracea L. ssp. italica) Inhibits Formation of the Anticancer Agent Sulforaphane

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• 作者：Nathan V. Matusheski ; Ranjan Swarup ; John A. Juvik ; Richard Mithen ; Malcolm Bennett ; and Elizabeth H. Jeffery
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2006
• 出版时间：March 22, 2006
• 年：2006
• 卷：54
• 期：6
• 页码：2069 - 2076
• 全文大小：344K
• 年卷期：v.54,no.6(March 22, 2006)
• ISSN：1520-5118

文摘

In some cruciferous plants, epithiospecifier protein (ESP) directs myrosinase (EC 3.2.3.1)-catalyzedhydrolysis of alkenyl glucosinolates toward epithionitrile formation. Here, for the first time, we showthat ESP activity is negatively correlated with the extent of formation of the health-promotingphytochemical sulforaphane in broccoli (Brassica oleracea L. ssp. italica). A 43 kDa protein withESP activity and sequence homology to the ESP of Arabidopsis thaliana was cloned from the broccolicv. Packman and expressed in Escherichia coli. In a model system, the recombinant protein not onlydirected myrosinase-dependent metabolism of the alkenyl glucosinolate epi-progoitrin [(2S)-2-hydroxy-3-butenyl glucosinolate] toward formation of an epithionitrile but also directed myrosinase-dependenthydrolysis of the glucosinolate glucoraphanin [4-(methylsulfinyl)butyl glucosinolate] to form sulforaphane nitrile, in place of the isothiocyanate sulforaphane. The importance of this finding is that,whereas sulforaphane has been shown to have anticarcinogenic properties, sulforaphane nitrile hasnot. Genetic manipulation designed to attenuate or eliminate expression of ESP in broccoli couldincrease the fractional conversion of glucoraphanin to sulforaphane, enhancing potential healthbenefits.Keywords: Epithiospecifier protein; Brassica oleracea; broccoli; glucosinolates; sulforaphane; sulforaphane nitrile