Isolation and enzimatic characterization of a Phospholipase A2 present in Rhinella schneideri toad poison

Abstract

The toad family Bufonidae, which belongs the species Rhinella schneideri, is considered the most toxic among the anurans. It's toxicicity depends on several components of the mucous and granular secretion. Mucous secretion is more related to the skin hidratation of the toad, preventing its dryness, and also acting on the gas exchange. Besides that, studies indicate that the secretion obtained from this gland is related to micro-organism proliferation on epidermis. In contrast, the secretions obtained from granulous glands, are related, mainly, to the defence against predators. The mucous secretion composition of toads is, in majority, of biogenic amines and steroidal derivatives. Nevertheless, recent researches also indicate the presence of other components, such as phospholipase A2 (PLA2), on the R. schenideri mucous secretion, which are similar to the ones detected on snake venoms. Amongst other functions, PLA2 from snake venoms are capable to induce oedema and has a myotoxic and antimicrobial activity. Since there are no studies about PLA2 on the poison of Rhinella schneideri species, this project has as objective the structural characterization of this enzyme and the determination of its possible functions on the poisoning from functional assays. The enzyme will be isolated by chromatographic procedures from the mucous secretion of the R. schneideri, and its structure will be analysed by amino terminal sequence and mass spectroscopy assays. Moreover, the PLA2 antimicrobial actions is will be evaluated by the minimal inhibitory concentration (MIC) on Gram negatives, Gram positives bacterias and yeast. This Project will expand the knowledge about the composition of this poison and about the molecular and functional characteristics of this enzyme.