Metais pesados interferem na atividade de enzimas do tipo lacases do camarão Litopenaeus vannamei?

Abstract

The contamination of aquatic environments with potentially toxic chemical elements and organic compounds (pesticides, hydrocarbons, dyes, etc.) has been notorious due to the industrial activity. In such a context, there has been an increase regarding the use of shrimp farming residues as sources of molecules with applications in bioremediation, such as laccase enzymes, which present a degradation activity of various contaminants such as aromatic hydrocarbons, phenols, pesticides, dyes, among others. However, such contaminants are discarded in water along with potentially toxic chemical elements and these can interfere in the enzymatic activity of enzyme bioremediation in such a variety of contaminants. Then, it is important to understand whether the enzymes will remain active even with the presence of potentially toxic chemical elements. Consequently, this work aims to evaluate the effect of potentially toxic chemical elements on laccase enzymes from the crude extracts from the shrimp Litopenaeus vannamei hepatopancreas. The effect of metals was also evidenced in metalloproteinases in the same extract to understand whether the presence of these enzymes interfere on the interaction of metals with laccases. To determine the effect of the potentially toxic metals (nickel, mercury, copper, cadmium and zinc in concentrations between 0.001 and 10 mM), they were incubated (separately) with the extracts. Subsequently, the percentage of the residual activity of laccases and metalloproteinases was verified compared with a control without potentially toxic metals (100%). None of the potentially toxic metals between 0.001 and 1 mM (concentration above the allowable values) were able to inhibit the tested enzymes. Furthermore, 10 mM of nickel chloride also were not able to inhibit the activity of laccases and metalloproteinases. On the other hand, the 10 mM chlorides of mercury, copper and cadmium were able to significantly increase laccase’s activity, while chlorides of mercury and copper inhibited metalloproteinases. In its turn, the 10 mM zinc sulfate inhibited both laccases and metalloproteinases. Therefore, it is concluded that the majority of the tested potentially toxic metals were able to interfere in the laccase enzymes activity in the extract of hepatopancreas from L. vannamei.