"Análise da composição da peçonha de Apis mellifera do Mato Grosso do Sul e os efeitos cinéticos da melitina na atividade da enzima Na⁺,K⁺-ATPase. "

Abstract

In Brazil, Africanized honey bees, Apis mellifera, are responsible for a large number of accidents involving humans. These accidents are more serious in cases of multiple stings or when there are individuals allergic to the venom. The composition of honey bee venom varies according to genetic diversity and environmental factors such as climate, season and diet. Apitoxin contains more than 50 molecules, including melittin and phospholipase A2, which play important roles in toxicity. Na, K-ATPase EC (7.2.2.13) is an enzyme with several functions in the body, from balancing ions to reabsorption of water and sodium in the kidneys. Melittin has been described as an inhibitor of this enzyme, but its inhibition mechanism has few studies. The objective of this study was to characterize the composition of A. mellifera venom from Mato Grosso do Sul and to verify the biological and biochemical effects of the interaction between melittin and Na, K-ATPase. To obtain apitoxin, an apitoxin collector was developed using electrostimulation extraction method, totaling 14 extractions. By electrophoresis, some components are suggested in the venom of A. mellifera from Mato Grosso do Sul, such as phospholipase A2, hyaluronidase, acid phosphatase, MRJP, α-glucosidase and melittin. In the apitoxin, phospholipase activity was identified in liquid and solid state assays. Furthermore, crude venom inhibits Na,K-ATPase activity with IC50 of 12.39 μg/mL and KI of 12.63 μg/mL. In silico studies show that melittin compromises the conformational change from E2P to E2 of Na,K-ATPase, increases the length of the salt bond between critical amino acid residues (Glu223 and Arg551), and this interaction also influences the conformation of Mg+2-binding regions, an essential cofactor of the enzyme. Thus, the inhibition seen in vitro can be explained by the interaction between melittin and Na,K-ATPase in silico. In that interaction, melittin binds to a region near the TGES motif. In conclusion, the understanding of these mechanisms in silico was important to clear the process of Na,K-ATPase inhibition by melittin, contributing to studies on the effects of apitoxin on the nervous and renal systems. Furthermore, the study of the composition of the venom of A. mellifera from Mato Grosso do Sul might enrich the database of biochemical components in the venom of the Africanized honey bee of Brazil, this can help in the development of antivenoms and medicinal or therapeutic innovations using apitoxin.