Prospecção in silico de novos peptídeos antimicrobianos a partir de fragmentos proteolíticos de leite bovino

Abstract

The nutrition quality improvement may play beneficial physiological effects and also reduce the risk of certain diseases. Milk contributes to the recommended nutrients intake and could promote health through its biologically active components, adding many features to nutrition. Otherwise, the search for a new broad-spectrum antibiotic action has increased in last decades due to to the increased number of bacteria resistant to conventional antibiotics. In this view, bovine milk proteins are promising antimicrobial peptides (AMPs) sources, which are inactive when are located inside of a large protein sequence and could be released by digestive enzymes during gastrointestinal transit. Here, those peptide sequences were obtained from free databases and summarily cleaved by gastrointestinal enzymes (pepsin, trypsin and chymotrypsin). This virtual cleavage provided a wide number of peptides that were analyzed and selected according to the inherent AMPs properties, such as size, charge, composition, hydrophobicity, hydrophobic moment and structuring. Five peptides (lactof01, lactof02, A_lacto01, serumA01 e serumA02) were selected, being their three-dimensional struture construted by homology modeling and validated through web servers. These peptides were synthesized and in vitro tested against Gram-positives (Staphylococcus aureus) and Gram-negatives (Escherichia coli e Klebsiella pneumoniae) microorganims. The peptides exhibited low antimicrobial activity. Nevertheless it was found that lactof02 was the most active against Gramnegatives and A_lact01 was the most active against Gram-positives. The hemolytic assays indicated that the peptides showed variable hemolytic activity. Through in vitro analisys of tests it was possible to verify that global and intrinsic peptides hydrophobicity seems to be crucial for modulation of antimicrobial and hemolytic activities.