Midgut cysteineproteinase activity in the velvetb

Authors: E G Mendonça M G A Oliveira L E Visôtto R N C Guedes

Publish Date: 2011/11/19

Volume: 85, Issue: 1, Pages: 117-123

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Abstract

Proteinase inhibitors are currently targeted as potential insect control agents but adaptation to proteinase inhibitors is a recognized limitation to such approach requiring the understanding of how phytophagous species can cope with such compounds The velvetbean caterpillar Anticarsia gemmatalis is a key pest of soybean and welladapted to its host proteinase inhibitors which is rich in serineproteinase inhibitors particularly trypsinlike proteinase inhibitors As the expression of cysteine proteinases in the midgut of the velvetbean caterpillar is a potential adaptation to circumvent its host defense we assessed and characterized the digestive cysteineproteinase activity from velvetbean caterpillars Significant soluble and membranebound proteolytic activity was obtained and was consistent with those of cysteine proteinases based on the substrate and inhibitors used for their characterization The K m and V max values obtained were 235 ± 050 mM and 4089 ± 668 nmol min−1 mg−1 for the soluble proteinases and 033 ± 003 mM and 2454 ± 067 nmol min−1 mg−1 for the membranebound proteinases range of values also consistent with cysteine proteinases Therefore the proteolytic activity observed in the velvetbean caterpillar midgut is consistent with that of cysteine proteinases providing preliminary support for the contention of their potential involvement mitigating the negative effects of serineprotease inhibitors in this speciesThe authors thank the financial support provided by the Minas Gerais State Foundation of Research Aid FAPEMIG the National Council of Scientific and Technological Development CNPq the CAPES Foundation and the INCT initiative FAPEMIGCNPq/MCT The provision of the initial stock population by EMBRAPA Soja was also greatly appreciated

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