A Kunitz-type inhibitor of coleopteran proteases, isolated from Adenanthera pavonina L. seeds and its effect on Callosobruchus maculatus |
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| Authors: | Macedo Maria Lígia Rodrigues de Sá Claudia Mara Freire Maria Das Graças Machado Parra José Roberto Postali |
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| Institution: | Laboratório de Purifica??o de Proteínas e suas Fun??es Biológicas, Departamento de Ciências Naturais, Universidade Federal de Mato Grosso do Sul, CP 210, CEP 79603-011,Três Lagoas, MS, Brazil. bioplant@terra.com.br |
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| Abstract: | The cowpea weevil Callosobruchus maculatus is one of the major pests of Vigna unguiculata cowpea. Digestion in the cowpea weevil is facilitated by high levels of cysteine and aspartic acid proteinases. Plants synthesize a variety of molecules, including proteinaceous proteinase inhibitors, to defend themselves against attack by insects. In this work, a trypsin inhibitor (ApTI) isolated from Adenanthera pavonina seeds showed activity against papain. The inhibition of papain by ApTI was of the noncompetitive type, with a K(i) of 1 microM. ApTI was highly effective against digestive proteinases from C. maculatus, Acanthoscelides obtectus (bean weevil), and Zabrotes subfasciatus (Mexican bean weevil) and was moderately active against midgut proteinases from the boll weevil Anthonomus grandis and the mealworm Tenebrio molitor. In C. maculates fed an artificial diet containing 0.25% and 0.5% ApTI (w/w), the latter concentration caused 50% mortality and reduced larval weight gain by approximately 40%. The action of ApTI on C. maculatus larvae may involve the inhibition of ApTI-sensitive cysteine proteinases and binding to chitin components of the peritrophic membrane (or equivalent structures) in the weevil midgut. |
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