Characterisation of recombinant epithiospecifier protein and its over-expression in Arabidopsis thaliana

Epithiospecifier protein (ESP) together with myrosinase (MYR) and ferrous ions (Fe 2+) catalyses formation of epithionitriles. Ectopic expression of ESP in A. thaliana altered the glucosinolate (4-methylsulfinylbutylglucosinolate) product profile from 1-isothiocyanato-4-(methylsulfinyl)butane towards the 5-(methylsulfinyl)pentanenitrile. Recombinant ESP was used to examine the formation of 3-hydroxy-3-(thiiran-2-yl)propanenitrile, 2-(thiiran-2-yl)acetonitrile and 5-(methylsulfinyl)pentanenitrile from their respective glucosinolates. Epithiospecifier protein (ESP) is a protein that catalyses formation of epithionitriles during glucosinolate hydrolysis. In vitro assays with a recombinant ESP showed that the formation of epithionitriles from alkenylglucosinolates is ESP and ferrous ion dependent. Nitrile formation in vitro however does not require ESP but only the presence of Fe(II) and myrosinase. Ectopic expression of ESP in Arabidopsis thaliana Col-5 under control of the strong viral CaMV 35S promoter altered the glucosinolate product profile from isothiocyanates towards the corresponding nitriles.