Aislamiento, actividad biológica y caracterización bioquímica de lectina de semillas de chenopodium quinoa willd. (cv. Salcedo-INIA)
Palavras-chave:
lectina, Chenopodium quinoa, bactoaglutinación, actividad insecticidaSinopse
Las lectinas actúan como moléculas de reconocimiento celular, y probablemente en la defensa vegetal. La CqLEC, lectina de Ch. quinoa cv Salcedo INIA, fue aislada, purificada y caracterizada a partir de 70 g de semillas a través de extracción salina, y la combinación de dos cromatografías de exclusión molecular tales como las de Sephadex G-100 y G-75 logrando obtenerse 5,53 mg/ml de proteína con actividad hemaglutinante, así como por HPLC de fase reversa a los 32 minutos con 54 % de tampón B indicando que poseía un bajo número de residuos hidrofóbicos en su estructura. Asimismo, el SDS-PAGE demostró que la lectina purificada fue homogénea ya que presentaba un solo componente correspondiente a una proteína de 12,82 kDa. Siendo que la CqLEC aglutinó eritrocitos humanos del grupo sanguíneo “O Rh+” con una CMH de 1,95 mg/ml, inhibido por fucosa (0,78 mM) y el agente quelante EGTA (0,1 mM), esto indicaba que sería una lectina ligadora de fucosa dependiente de iones divalentes tales como el calcio o el manganeso. Por otra parte, esta proteína mostró una bactoaglutinación específica para E. coli (CMB igual a 200 mg/ml), así como actividad insecticida en contra de larvas de Symmetrischema plaesiosema (1000 ppm of CqLEC, P < 0,05). El análisis completo de aminoácidos reveló que la CqLEC es una lectina de naturaleza ácida (70,54 % de residuos hidrofílicos y 29,46 % de residuos hidrofóbicos), prevaleciendo el ácido glutámico (33 %), con una masa molecular de 12,859 kDa. Por estudio de homología secuencial se determinó que ésta pertenece a la familia de lectinas vegetales de Leguminosas, mostrando 82,1 % de similitud con el precursor de la aglutinina I extraída a partir de la corteza de Cladrastis kentukea. La CqLEC también presentó residuos altamente conservados en su estructura tales como Leu 4, Ser 6 y Phe 7.
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