Isolamento, purificação, caracterização e atividade biológica da lectina da fração das albuminas de sementes de Acacia farnesiana (L) Willd. (Leguminoseae - Mimosoidae)

Abstract

The Acacia genus, inserted in the Mimosoideae subfamily, is among the most important genera through the ecological point of view, possessing the ability to adapt to almost all kinds of weather and soil. Within this genus many biological activities were reported, such as: inhibition of platelet aggregation, potent inhibition ofciclooxigenase's activity, besides the astringent, analgesic and antibacterial activities, among others. Several studies about lectins have been developed with Leguminosae family members, however within the Acacieae tribe, only the Acacia constricta lectin has been investigated. The lectin of the albumin fraction of Acacia famesiana seeds (AFAL) is capable of binding to a chitin column, where is verified the different interaction degrees presented, probably due to the particularity showed by this lectin in oligomerizing in a time of dissolution dependent way. This lectin cannot be inhibited by Nacetylglucosamine or by a carbohydrate comprising 6 to 8 residues of Nacetylglucosamine; its isoeletric point is at pH 4.0; its eletroforetic pattern shows two bands with 50 and 29 kDa of apparent molecular mass, confirmed by its mass spectra (MALDI-ToF/MS), that presented the monomeric form with 24.2 kDa and the dimeric fonn with 50.0 kDa, fact that points to the possibility of this lectin being a tetramer with identical subunits; its N-terminal sequence has 87% of similanty with Acacia constricta lectin and 62.1% with the one from Phaseolus vulgaris. The biological activities assays performed with AFAL indicated that this lectin is able to aggregate platelets, has proinflammatory activity and acts as antinociceptive agent. Moreover, the experiments with phytopathogens demonstrated that it has the ability to inhibit phytobacteria growth (Xanthomonas axonopodis pv. passiflorae and Clavibacter michiganensis, michiganensis) and to interfere in the phytonematode's (Meloidogyne) incognita eclosion and movement.