Epithiospecifier protein from broccoli (Brassica oleracea L. ssp. italica) inhibits formation of the anticancer agent sulforaphane.
In some cruciferous plants, epithiospecifier protein (ESP) directs myrosinase (EC 3.2.3.1)-catalyzed hydrolysis of alkenyl glucosinolates toward epithionitrile formation. Here, for the first time, we show that ESP activity is negatively correlated with the extent of formation of the health-promoting phytochemical sulforaphane in broccoli (Brassica oleracea L. ssp. italica). A 43 kDa protein with ESP activity and sequence homology to the ESP of Arabidopsis thaliana was cloned from the broccoli cv. Packman and expressed in Escherichia coli. In a model system, the recombinant protein not only directed myrosinase-dependent metabolism of the alkenyl glucosinolate epi-progoitrin [(2S)-2-hydroxy-3-butenyl glucosinolate] toward formation of an epithionitrile but also directed myrosinase-dependent hydrolysis 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 has not. Genetic manipulation designed to attenuate or eliminate expression of ESP in broccoli could increase the fractional conversion of glucoraphanin to sulforaphane, enhancing potential health benefits.
Department of Food Science and Human Nutrition, University of Illinois, 905 South Goodwin Avenue, Urbana, Illinois 61801, USA.
Nathan V
NV
Matusheski
Ranjan
R
Swarup
John A
JA
Juvik
Richard
R
Mithen
Malcolm
M
Bennett
Elizabeth H
EH
Jeffery
D000595:Amino Acid Sequence; D016588:Anticarcinogenic Agents; D029681:Arabidopsis Proteins / Q000737:chemistry; D001937:Brassica / Q000737:chemistry* / Q000201:enzymology / Q000378:metabolism; D003001:Cloning, Molecular; D004798:Enzymes / Q000737:chemistry; D004926:Escherichia coli; D015870:Gene Expression; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors; D017879:Isothiocyanates; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D017385:Sequence Homology; D013454:Sulfoxides; D013861:Thiocyanates / Q000037:antagonists & inhibitors* / Q000378:metabolism
D016588:Anticarcinogenic Agents; D029681:Arabidopsis Proteins; D004798:Enzymes; D017879:Isothiocyanates; D010940:Plant Proteins; D013454:Sulfoxides; D013861:Thiocyanates; C450151:epithiospecifier protein, Arabidopsis; D006026:Glycoside Hydrolases; C022739:thioglucosidase; C016766:sulforaphane