TAILIEUCHUNG - Báo cáo khoa học: Brassinin oxidase, a fungal detoxifying enzyme to overcome a plant defense – purification, characterization and inhibition

Blackleg fungi [Leptosphaeria maculans(asexual stage Phoma lingam) and Leptosphaeria biglobosa] are devastating plant pathogens with well-estab-lished stratagems to invade crucifers, including the production of enzymes that detoxify plant defenses such as phytoalexins. | ỊFEBS Journal Brassinin oxidase a fungal detoxifying enzyme to overcome a plant defense - purification characterization and inhibition M. S. C. Pedras Zoran Minic and Mukund Jha Department of Chemistry University of Saskatchewan Canada Keywords brassinin oxidase camalexin detoxifying enzyme Leptosphaeria maculans phytoalexin Correspondence M. S. C. Pedras Department of Chemistry University of Saskatchewan 110 Science Place Saskatoon Saskatchewan S7N 5C9 Canada Fax 1 306 966 4730 Tel 1 306 966 4772 E-mail Recived 24 April2008 revised 17 May 2008 accepted 21 May 2008 doi Blackleg fungi Leptosphaeria maculans asexual stage Phoma lingam and Leptosphaeria biglobosa are devastating plant pathogens with well-established stratagems to invade crucifers including the production of enzymes that detoxify plant defenses such as phytoalexins. The significant roles of brassinin both as a potent crucifer phytoalexin and a biosynthetic precursor of several other plant defenses make it critical to plant fitness. Brassinin oxidase a detoxifying enzyme produced by L. maculans both in vitro and in planta catalyzes the detoxification of brassinin by the unusual oxidative transformation of a dithiocarbamate to an aldehyde. Purified brassinin oxidase has an apparent molecular mass of 57 kDa is approximately 20 glycosylated and accepts a wide range of cofactors including quinones and flavins. Purified brassinin oxidase was used to screen a library of brassinin analogues and crucifer phytoalexins for potential inhibitory activity. Unexpectedly it was determined that the crucifer phytoalexins camalexin and cyclobrassinin are competitive inhibitors of brassinin oxidase. This discovery suggests that camalexin could protect crucifers from attacks by L. maculans because camalexin is not metabolized by this pathogen and is a strong mycelial growth inhibitor. Microbial plant pathogens display a variety of successful strategies to invade plant .

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