title: A young root-specific gene (ArMY2) from horseradish encoding a MYR II myrosinase with kinetic preference for the root-specific glucosinolate gluconasturtiin.
abstract: The pungent taste of horseradish is caused by isothiocyanates which are released from glucosinolates by myrosinases. These enzymes are encoded by genes belonging to one of two subfamilies, termed MYR I and MYR II, respectively. A MYR II-type myrosinase gene was identified for the first time in horseradish. The gene termed ArMY2 was only expressed in young roots. A full-length cDNA encoding a myrosinase termed ArMy2 was isolated and heterologously expressed in Pichia pastoris. The recombinant His-tagged enzyme was characterized biochemically. Substrate affinity was 5 times higher towards gluconasturtiin than towards sinigrin. Gluconasturtiin was found to be the most abundant glucosinolate in young horseradish roots while sinigrin dominated in storage roots and leaves. This indicates that a specialized glucosinolate-myrosinase defense system might be active in young roots.
authors: Department Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Staudtstr. 5, D-91058 Erlangen, Germany.
authors: Andreas
authors: A
authors: Loebers
authors: Department Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Staudtstr. 5, D-91058 Erlangen, Germany.
authors: Frieder
authors: F
authors: Müller-Uri
authors: Department Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Staudtstr. 5, D-91058 Erlangen, Germany; ECROPS, Erlangen Center of Plant Science, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schlossplatz 4, D-91054 Erlangen, Germany. Electronic address: wkreis@biologie.uni-erlangen.de.
authors: Wolfgang
authors: W
authors: Kreis
mesh_terms: D031215:Armoracia / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D005961:Glucosinolates / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*
chemical_list: D005961:Glucosinolates; C443697:gluconasturtiin; D006026:Glycoside Hydrolases; C022739:thioglucosidase
keywords: Armoracia rusticana; Brassicaceae; Enzyme kinetics; Glucosinolate; Horseradish; Myrosinase