Efeito de um inibidor de tripsina de sementes de Plathymenia foliolosa sobre o desenvolvimento e atividade enzimatica de Anagasta kuehniella / Effect of a trypsin inhibitor from Plathymenia foliolosa seeds on Anagasta kuehniella development and enzymatic activity

AUTOR(ES)

Vanessa da Silveira Ramos

DATA DE PUBLICAÇÃO

2008

RESUMO

Proteinase inhibitors (PIs) are widely distributed in animals, microorganisms, and plants. Plant PIs are generally small proteins that have mainly been described as occurring in storage tissues, such as tubers and seeds, but they have also been found in the aerial parts of plants, in the leaves, flowers and roots. The possible roles suggested for seed proteinase inhibitors include the function as a part of the plant defensive system against pest via inhibition of their proteolytic enzymes. The activity of PIs is due to their capacity to form stable complexes with target proteases, blocking, altering or preventing access to the enzyme active site. Lepidoptera are often insects which attack a wide range of crops, causing damage high economic value. A. kuehniella is found worldwide, this insect attacks stored grains, and products of rice, oat, rye, corn and wheat. In this report, the pure inhibitor from seeds of Plathymenia foliolosa (Mimosoideae) – PFTI was monitoring by an insect bioassay its toxic activity toward A. kuehniella. The chronic ingestion of PFTI did result in a significant reduction in larval survival and weight (32.3% and 66.1% respectively) and also reduced the larval viability and the weight of pupae (35.7% and 9.1% respectively). The results from nutritional experiments realized with A. kuehniella larvae presented a reduction in efficiency of conversion of ingested food (ECI) and digested food (ECD), and an increase in approximate digestibility (AD) and CM (metabolic cost). To examine the protein effects on insect, the midgut proteinases of A. kuehniella larvae reared on artificial PI-free diet and on a diet containing PFTI at 0.7% were compared by using enzymatic assays and polyacrilamide gel electrophoresis. The fourth instar larvae reared on a diet containing PFTI showed a decrease in tryptic activity of gut and increase in tryptic activity of faeces, as confirmed by BApNA as substrate and by activity in gels. In addition, the tryptic activity in PFTI-fed larvae was sensitive to PFTI. These results suggest that PFTI have a potential antimetabolic effect when ingested by A. kuehniella.

ASSUNTO(S)

nutrição - indices anagasta inibidores de tripsina trypsin inhibitors plathymenia foliolosa nutrition

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