Purificação e caracterização bioquímica de um inibidor de protease cisteínica presente em sementes de Terminalia catappa, com potencial antimicrobiano frente a Staphylococcus aureus.

Abstract

Hospital infections are a public health problem, being caused by different microorganisms. Staphylococcus aureus is one of the bacteria that most causes hospital infection. It is resistance to antibiotics makes it impossible to control it and, therefore, the search for anti-S. aureus molecules in earthly flora and fauna sources are important and necessary, considering that commercially available antibiotics are not effective. The present study destined at purification and characterization a papain inhibitor, called TcPI-II, obtained from the plant species Terminalia catappa and evaluating it is antimicrobial activity against S. aureus. TcPI-II was purified from F80 ° C protein fraction prepared after protein extraction from mature T. catappa seeds using 50 mM Tris-HCl, pH 7.5, containing 200 mM NaCl and heat treatment at 80 ° C for 30 minutes, followed by chromatography of the soluble proteins recovered from ion exchange resin (DEAE-cellulose). The non-retained DEAE-cellulose protein fraction was homogeneous, with purification index of 8.67 and yield of 2.29%. SDS-PAGE revealed that this purified fraction (TcPI-II) had a molecular mass of 15.9 kDa and papain specificity, a cysteine protease. Inhibition kinetics were found to be a competitive inhibitor (IC50 1.56 × 10-6 M), with a Ki of 1.02 x 10-6 M. TcPI-II preserved it is inhibitory activity when tested on a wide range pH range (2.0-10.0) and temperature (30-100 °C), sustain it is papain inhibitory activity even when heated to 100 °C (0-120 min). At a concentration of 3, 14 x 10-8 M, TcPI-II was able to inhibit S. aureus growth by 86, 40%. Therefore, it can be suggested that TcPI-II has the potential to be used to combat infections caused by S. aureus, but there is a need for studies of it is a mechanism of action and safety tests for it is clinical use.