TAILIEUCHUNG - Báo cáo khoa học: Comparative biochemical characterization of nitrile-forming proteins from plants and insects that alter myrosinase-catalysed hydrolysis of glucosinolatesk

The defensive function of the glucosinolate–myrosinase system in plants of the order Capparales results from the formation of isothiocyanates when glucosinolates are hydrolysed by myrosinases upon tissue damage. In some glucosinolate-containing plant species, as well as in the insect herbivore Pieris rapae, protein factors alter the outcome of myrosinase-catalysed glu-cosinolate hydrolysis, leading to the formation of products other than isothiocyanates. | iFEBS Journal Comparative biochemical characterization of nitrile-forming proteins from plants and insects that alter myrosinase-catalysed hydrolysis of glucosinolates Meike Burow Jana Markert Jonathan Gershenzon and Ute Wittstock Max Planck Institute for ChemicalEcology Department of Biochemistry Jena Germany Keywords epithionitrile epithiospecifier protein glucosinolate nitrile nitrile-specifier protein Correspondence U. Wittstock Institut fur Pharmazeutische Biologie Technische Universitat Braunschweig Mendelssohnstr. 1 D-38106 Baunschweig Germany Fax 49 531 391 8104 Tel 49 531 391 5681 E-mail Received 1 March 2006 accepted 30 March 2006 doi The defensive function of the glucosinolate-myrosinase system in plants of the order Capparales results from the formation of isothiocyanates when glucosinolates are hydrolysed by myrosinases upon tissue damage. In some glucosinolate-containing plant species as well as in the insect herbivore Pieris rapae protein factors alter the outcome of myrosinase-catalysed glu-cosinolate hydrolysis leading to the formation of products other than isothiocyanates. To date two such proteins have been identified at the molecular level the epithiospecifier protein ESP from Arabidopsis thaliana and the nitrile-specifier protein NSP from P. rapae. These proteins share no sequence similarity although they both promote the formation of nitriles. To understand the biochemical bases of nitrile formation we compared some of the properties of these proteins using purified preparations. We show that both proteins appear to be true enzymes rather than allosteric cofactors of myrosinases based on their substrate and product specificities and the fact that the proportion of glucosinolates hydrolysed to nitriles does not remain constant when myrosinase activity varies. No stable association between ESP and myrosinase could be demonstrated during affinity chromatography nevertheless some proximity of

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