Purificação parcial, propriedades bioquímicas e cinéticas de α- amilases de populações de Sitophilus zeamais resistentes e susceptível a piretróides

• Autor(a) principal: Lopes, Kênia Viçoso Gomes
• Data de Publicação: 2008
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2416
• topic: Piretróides; Alfa amilase; Sitophilus zeamais; Pyrethroids; α-amylase; Sitophilus zeamais; CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA::ENZIMOLOGIA

Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), stands out as the main pest that attacks the stored grain causing great damages. The control of this insect is made mainly by insecticides, and the intensive use of those compounds took to the occurrence of several cases of resistance. The expression of the resistance to insecticides usually induces harmful effects in the insect. Populations of S. zeamais with susceptibilities different to insecticides can present larger efficiency in the digestion of the starch ingested by the largest α-amylase activity in resistant populations. That would make possible the insect a larger accumulation of nutrients in the fat body for maintenance of their defense components without causing damage to its growth and development. For obtaining of the purified α-amylases were made sequentially a precipitation with glycogen and an ion-exchange chromatography. The purified enzyme of the resistant population without cost presented an α-amylase activity similar to obtained her for the population susceptible and larger in relation to the resistant population with cost. The eluition profile regarding purification of the enzymes of the two resistant populations evidenced the presence of more than a peak with α-amylase activity suggesting the isoforms production with isoelectric points different. The purified α-amylases of the three populations presented a molecular mass of 53.6 kDa for SDS-PAGE. The largest activity in all of the populations was in pH 5.0 in a range of temperature from 30 to 40 °C. The inhibitor acarbose and the inhibitor extracted of wheat were shown effective in inhibiting the α-amylases partially and the amylase of the resistant population without cost showed less vulnerable to the inhibition. The resistant population without physiologic cost associate to the phenomenon of the resistance presented a larger activity and larger production of the enzyme when compared to the resistant population with cost and the susceptible population. The largest production of the enzyme would be making possible a larger energy stock in the fat body of the insects allowing the maintenance of the resistance mechanisms without compromise the other physiologic processes. In that way, the largest α-amylase levels would be contributing to mitigate the physiologic cost associate to the resistance mechanisms in the resistant population without cost of S. zeamais.