Nitrilase protein families in glucosinolate forming plants
MARKUS PIOTROWSKI
Ruhr-Universität Bochum
Lehrstuhl für Pflanzenphysiologie
ND3
Universitätsstraße 150
D-44801 Bochum
Markus.Piotrowski@ruhr-uni-bochum.de
http://www.ruhr-uni-bochum.de/pflaphy/Seiten/PG_Piotrowski_engl.html
Nitrilases are enzymes which catalyze the hydrolysis of nitriles to their corresponding nitriles or amides. Homologs of the nitrilase isoform NIT4 are widely distributed among higher plants. This enzyme catalyzes the hydrolysis of ß-cyano-L-alanine, an intermediate product of cyanide detoxification of higher plants, and has therefore a function within the primary metabolism. In addition to NIT4, other nitrilase-homologs are known from Brassicaceae; their proposed function lies within the catabolism of glucosinolates. Glucosinolates are secondary plant metabolites, which are mainly found in plants of the order Capparales. If plants are wounded, glucosinolates are released from their cellular stores and hydrolyzed by thio-glucosidases (syn. myrosinases). The final products of these reactions are, depending on special proteins present in the plant, isothiocyanates, thiocyanates, or nitriles. Due to the evolution of the glucosinolate-biosynthesis enzymes, different species may form a different spectrum of glucosinolates and, accordingly, different glucosinolate-derived nitriles. Within the scope of this proposal we want to investigate, if, to what extend, and how the nitrilases of glucosinolate-forming plants have evolved to match their proposed new substrates, the glucosinolate-derived nitriles. For this purpose we have gained sequence data for nitrilases from several species of the order Capparales to study their phylogenetic relationships. Cloning of the full set of nitrilases from Capsella rubella is in progress. These enzymes will be biochemically characterized and compared to the enzymes of Arabidopsis thaliana. In addition, nitrilase knockout- or RNAi-plants of Arabidopsis thaliana were generated, which will be analyzed regarding their glucosinolate catabolism.
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