Identificação de inibidores de proteinase do tipo Kunitz com atividade antimicrobiana em cormos de Xanthosoma blandum

Abstract

Nosocomial infection is a serious problem in world due to the development of antimicrobial resistance to conventional antibiotics. Otherwise the plants are exposed to a wide variety of potentially pathogenic organisms, generating a wide spectrum of antimicrobial proteins with bifunctional properties, also exerting the function of proteinase inhibitors. This study aims to evaluate the antibacterial activity of corms from 12 species of Xanthosoma genus against five human bacterial pathogens as well to elucidate the effective compound with antimicrobial and anti-proteinase activities. In this view, corms were extracted with a solution containing 0.6 M NaCl and 0.1 % HCl, followed by precipitation with (NH4)2SO4 (100%) and dialysis against distilled water (cut off 3.5 kDa), yielding the Protein Rich Fraction (FRP). Bioassays were performed in LB broth by using FRP (100 μg.mL-1), NaCl 0.85 % (C-) and chloramphenicol 40 μg.ml-1 (C +). PRF X . blandum was applied onto a semi-preparative column (Vydac C-18TP 522) HPLC. The major fraction 07 obtained, eluted in 49 % acetonitrile, showed a 62 % inhibition of f Salmonella typhimurium growth. Tris-Tricine gel analyses revealed a 24 kDa protein with 63 % of similarity to Kunitz-type inhibitors. This inhibitor also showed an anti-proteinase activity against bovine trypsin and also toward a pool of S. typhimurium proteinases, showing an inhibition of 63 and 85 % of the activity, respectively. Thus Xb-KTI the first bifunctional inhibitor described in corms with biotechnological potential for prospection and development of modeling drugs with activity against human pathogenic bacteria.