Purification and characterization of pterocarpan hydroxylase,a flavoprotein monooxygenase from the fungus Ascochyta rabiei involved in pterocarpan phytoalexin metabolism |
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Authors: | R. Tenhaken H. Ch. Salmen W. Barz |
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Affiliation: | (1) Lehrstuhl für Biochemie der Pflanzen, Westfälische Wilhelms-Universität, Hindenburgplatz 55, W-4400 Münster, Federal Republic of Germany |
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Abstract: | Crude protein extracts from the chickpea (Cicer arietinum) pathogenic fungus Ascochyta rabiei catalyze the hydroxylation of the pterocarpan phytoalexins medicarpin and maackiain to the corresponding 1a-hydroxy-1,4-diene-3-one derivatives. The enzyme reaction depends on NAD(P)H and molecular oxygen. Low amounts of FAD are necessary for maximal enzyme activity. The pterocarpan hydroxylase is a new flavoprotein monooxygenase with a molecular weight of 58 kDa in SDS-PAGE. The soluble enzyme can utilize NADH and NADPH with similar values for Km and Vmax respectively. The pterocarpan hydroxylase and a pterocarpan reductase (Mr 29 kDa; Höhl and Barz 1987) are constitutively expressed by A. rabiei isolates.Abbreviations AAS atomic absorption spectroscopy - BCS bathocuproindisulfonate - BSA bovine serum albumin - FAD flavin-adenine dinucleotide - FMN flavin-mononucleotide - Mr molecular weight - PAGE polyacrylamide gelelectrophoresis - pda pisatin demethylating ability - SDS sodium dodecylsulfate - Tris tris(hydroxymethyl)aminomethane |
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Keywords: | Metabolism Pterocarpan Phytoalexins Ascochyta rabiei Monooxygenase Flavoprotein |
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